Apparatus and method of random access procedure

ABSTRACT

A communication method and system for converging a fifth generation (5G) communication system for supporting higher data rates beyond a fourth generation (4G) system with a technology for Internet of things (IoT) are provided. The communication method and system may be applied to intelligent services based on the 5G communication technology and the IoT-related technology, such as smart home, smart building, smart city, smart car, connected car, health care, digital education, smart retail, security and safety services. A method for performing a random access procedure in a wireless communication system is provided.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is based on and claims priority under 35 U.S.C. §119(e) of a U.S. Provisional application Ser. No. 62/959,309, filed onJan. 10, 2020, in the U.S. Patent and Trademark Office, the disclosureof which is incorporated by reference herein in its entirety.

BACKGROUND 1. Field

The disclosure relates to an apparatus and a method of performing randomaccess procedure.

2. Description of Related Art

To meet the demand for wireless data traffic having increased sincedeployment of fourth generation (4G) communication systems, efforts havebeen made to develop an improved fifth generation (5G) or pre-5Gcommunication system. Therefore, the 5G or pre-5G communication systemis also called a ‘Beyond 4G Network’ or a ‘Post long term evolution(LTE) System’. The 5G communication system is considered to beimplemented in higher frequency (millimeter (mm) Wave) bands, e.g., 60gigahertz (GHz) bands, so as to accomplish higher data rates. Todecrease propagation loss of the radio waves and increase thetransmission distance, the beamforming, massive multiple-inputmultiple-output (MIMO), Full Dimensional MIMO (FD-MIMO), array antenna,an analog beam forming, large scale antenna techniques are discussed in5G communication systems. In addition, in 5G communication systems,development for system network improvement is under way based onadvanced small cells, cloud Radio Access Networks (RANs), ultra-densenetworks, device-to-device (D2D) communication, wireless backhaul,moving network, cooperative communication, Coordinated Multi-Points(CoMP), reception-end interference cancellation and the like. In the 5Gsystem, Hybrid Frequency Shift Keying (FSK) and Quadrature AmplitudeModulation (QAM) (FQAM) and sliding window superposition coding (SWSC)as an advanced coding modulation (ACM), and filter bank multi carrier(FBMC), non-orthogonal multiple access (NOMA), and sparse code multipleaccess (SCMA) as an advanced access technology have been developed.

The Internet, which is a human centered connectivity network wherehumans generate and consume information, is now evolving to the Internetof Things (IoT) where distributed entities, such as things, exchange andprocess information without human intervention. The Internet ofEverything (IoE), which is a combination of the IoT technology and theBig Data processing technology through connection with a cloud server,has emerged. As technology elements, such as “sensing technology”,“wired/wireless communication and network infrastructure”, “serviceinterface technology”, and “Security technology” have been demanded forIoT implementation, a sensor network, a Machine-to-Machine (M2M)communication, Machine Type Communication (MTC), and so forth have beenrecently researched. Such an IoT environment may provide intelligentInternet technology services that create a new value to human life bycollecting and analyzing data generated among connected things. IoT maybe applied to a variety of fields including smart home, smart building,smart city, smart car or connected cars, smart grid, health care, smartappliances and advanced medical services through convergence andcombination between existing Information Technology (IT) and variousindustrial applications.

In line with this, various attempts have been made to apply 5Gcommunication systems to IoT networks. For example, technologies such asa sensor network, Machine Type Communication (MTC), andMachine-to-Machine (M2M) communication may be implemented bybeamforming, MIMO, and array antennas. Application of a cloud RadioAccess Network (RAN) as the above-described Big Data processingtechnology may also be considered to be as an example of convergencebetween the 5G technology and the IoT technology.

The above information is presented as background information only toassist with an understanding of the disclosure. No determination hasbeen made, and no assertion is made, as to whether any of the abovemight be applicable as prior art with regard to the disclosure.

SUMMARY

Aspects of the disclosure are to address at least the above-mentionedproblems and/or disadvantages and to provide at least the advantagesdescribed below. Accordingly, an aspect of the disclosure is to providea communication method and system for converging a fifth generation (5G)communication system for supporting higher data rates beyond a fourthgeneration (4G) system.

Additional aspects will be set forth in part in the description whichfollows and, in part, will be apparent from the description, or may belearned by practice of the presented embodiments.

In accordance with an aspect of the disclosure, a method performed by aterminal for 2-step random access procedure in a wireless communicationsystem is provided. The method includes identifying that contention-freerandom access resources for 2-step random access is not configured,identifying whether one of a first preamble group or a second preamblegroup is selected for a previous random access preamble transmissionattempt during the 2-step random access procedure, in case that the oneof the first preamble group or the second preamble group is selected,selecting a same preamble group used for the previous random accesspreamble transmission attempt, for transmitting a contention-basedrandom access preamble on a physical random access channel (PRACH), andtransmitting, to a base station, a message including the PRACH and aphysical uplink shared channel (PUSCH).

In accordance with another aspect of the disclosure, a terminal for2-step random access procedure in a wireless communication system isprovided. The terminal includes a transceiver and a controller coupledwith the transceiver and configured to control to identify thatcontention-free random access resources for 2-step random access is notconfigured, identify whether one of a first preamble group or a secondpreamble group is selected for a previous random access preambletransmission attempt during the 2-step random access procedure, in casethat the one of the first preamble group or the second preamble group isselected, select a same preamble group used for the previous randomaccess preamble transmission attempt, for transmitting acontention-based random access preamble on a physical random accesschannel (PRACH), and transmit, to a base station, a message includingthe PRACH and a physical uplink shared channel (PUSCH).

Other aspects, advantages, and salient features of the disclosure willbecome apparent to those skilled in the art from the following detaileddescription, which, taken in conjunction with the annexed drawings,discloses various embodiments of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of certainembodiments of the disclosure will be more apparent from the followingdescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 shows an operation for explaining an example of early datatransmission (EDT) according to an embodiment of the disclosure;

FIG. 2 shows an operation for explaining another example of EDTaccording to an embodiment of the disclosure;

FIG. 3 illustrates next generation RAN (NG-RAN) architecture supportingPC5 interface according to an embodiment of the disclosure;

FIG. 4 illustrates an embodiment of user equipment (UE) operation whenscheduling mode is changed from M2 to M1 for one or more sidelinklogical channels (SL LCHs) according to an embodiment of the disclosure;

FIG. 5 illustrates another embodiment of UE operation when schedulingmode is changed from M2 to M1 for one or more SL LCHs according to anembodiment of the disclosure;

FIG. 6 illustrates another embodiment of UE operation when schedulingmode is changed from M2 to M1 for one or more SL LCHs according to anembodiment of the disclosure;

FIG. 7 illustrates another embodiment of UE operation when schedulingmode is changed from M2 to M1 for one or more SL LCHs according to anembodiment of the disclosure;

FIG. 8 illustrates an embodiment of UE operation when scheduling mode ischanged from M1 to M2 for one or more SL LCHs according to an embodimentof the disclosure;

FIG. 9 illustrates another embodiment of UE operation when schedulingmode is changed from M1 to M2 for one or more SL LCHs according to anembodiment of the disclosure;

FIG. 10 is a block diagram of a UE according to an embodiment of thedisclosure; and

FIG. 11 is a block diagram of a base station according to an embodimentof the disclosure.

Throughout the drawings, like reference numerals will be understood torefer to like parts, components, and structures.

DETAILED DESCRIPTION

The following description with reference to the accompanying drawings isprovided to assist in a comprehensive understanding of variousembodiments of the disclosure as defined by the claims and theirequivalents. It includes various specific details to assist in thatunderstanding but these are to be regarded as merely exemplary.Accordingly, those of ordinary skill in the art will recognize thatvarious changes and modifications of the various embodiments describedherein can be made without departing from the scope and spirit of thedisclosure. In addition, descriptions of well-known functions andconstructions may be omitted for clarity and conciseness.

The terms and words used in the following description and claims are notlimited to the bibliographical meanings, but, are merely used by theinventor to enable a clear and consistent understanding of thedisclosure. Accordingly, it should be apparent to those skilled in theart that the following description of various embodiments of thedisclosure is provided for illustration purpose only and not for thepurpose of limiting the disclosure as defined by the appended claims andtheir equivalents.

It is to be understood that the singular forms “a,” “an,” and “the”include plural referents unless the context clearly dictates otherwise.Thus, for example, reference to “a component surface” includes referenceto one or more of such surfaces.

By the term “substantially” it is meant that the recited characteristic,parameter, or value need not be achieved exactly, but that deviations orvariations, including for example, tolerances, measurement error,measurement accuracy limitations and other factors known to those ofskill in the art, may occur in amounts that do not preclude the effectthe characteristic was intended to provide.

It is known to those skilled in the art that blocks of a flowchart (orsequence diagram) and a combination of flowcharts may be represented andexecuted by computer program instructions. These computer programinstructions may be loaded on a processor of a general purpose computer,special purpose computer, or programmable data processing equipment.When the loaded program instructions are executed by the processor, theycreate a means for carrying out functions described in the flowchart.Because the computer program instructions may be stored in a computerreadable memory that is usable in a specialized computer or aprogrammable data processing equipment, it is also possible to createarticles of manufacture that carry out functions described in theflowchart. Because the computer program instructions may be loaded on acomputer or a programmable data processing equipment, when executed asprocesses, they may carry out operations of functions described in theflowchart.

A block of a flowchart may correspond to a module, a segment, or a codecontaining one or more executable instructions implementing one or morelogical functions, or may correspond to a part thereof. In some cases,functions described by blocks may be executed in an order different fromthe listed order. For example, two blocks listed in sequence may beexecuted at the same time or executed in reverse order.

In this description, the words “unit”, “module” or the like may refer toa software component or hardware component, such as, for example, afield-programmable gate array (FPGA) or an application-specificintegrated circuit (ASIC) capable of carrying out a function or anoperation. However, a “unit”, or the like, is not limited to hardware orsoftware. A unit, or the like, may be configured so as to reside in anaddressable storage medium or to drive one or more processors. Units, orthe like, may refer to software components, object-oriented softwarecomponents, class components, task components, processes, functions,attributes, procedures, subroutines, program code segments, drivers,firmware, microcode, circuits, data, databases, data structures, tables,arrays or variables. A function provided by a component and unit may bea combination of smaller components and units, and may be combined withothers to compose larger components and units. Components and units maybe configured to drive a device or one or more processors in a securemultimedia card.

Prior to the detailed description, terms or definitions necessary tounderstand the disclosure are described. However, these terms should beconstrued in a non-limiting way.

The “base station (BS)” is an entity communicating with a user equipment(UE) and may be referred to as BS, base transceiver station (BTS), nodeB (NB), evolved NB (eNB), access point (AP), fifth generation (5G) NB(5gNB), or next generation NB (gNB).

The “UE” is an entity communicating with a BS and may be referred to asUE, device, mobile station (MS), mobile equipment (ME), or terminal.

In the recent years several broadband wireless technologies have beendeveloped to meet the growing number of broadband subscribers and toprovide more and better applications and services. The second generationwireless communication system has been developed to provide voiceservices while ensuring the mobility of users. Third generation wirelesscommunication system supports not only the voice service but also dataservice. In recent years, the fourth wireless communication system hasbeen developed to provide high-speed data service. However, currently,the fourth generation wireless communication system suffers from lack ofresources to meet the growing demand for high speed data services. So,fifth generation wireless communication system (also referred as nextgeneration radio or new radio (NR)) is being developed to meet thegrowing demand for high speed data services, support ultra-reliabilityand low latency applications.

The fifth generation wireless communication system supports not onlylower frequency bands but also in higher frequency (mmWave) bands, e.g.,10 GHz to 100 GHz bands, so as to accomplish higher data rates. Tomitigate propagation loss of the radio waves and increase thetransmission distance, the beamforming, massive Multiple-InputMultiple-Output (MIMO), Full Dimensional MIMO (FD-MIMO), array antenna,an analog beam forming, large scale antenna techniques are beingconsidered in the design of fifth generation wireless communicationsystem. In addition, the fifth generation wireless communication systemis expected to address different use cases having quite differentrequirements in terms of data rate, latency, reliability, mobility etc.However, it is expected that the design of the air-interface of thefifth generation wireless communication system would be flexible enoughto serve the UEs having quite different capabilities depending on theuse case and market segment the UE cater service to the end customer.Few example use cases the fifth generation wireless communication systemwireless system is expected to address is enhanced Mobile Broadband(eMBB), massive Machine Type Communication (m-MTC), ultra-reliable lowlatency communication (URLLC) etc. The eMBB requirements like tens ofGbps data rate, low latency, high mobility so on and so forth addressthe market segment representing the wireless broadband subscribersneeding internet connectivity everywhere according to the related art,all the time and on the go. The m-MTC requirements like very highconnection density, infrequent data transmission, very long batterylife, low mobility address so on and so forth address the market segmentrepresenting the Internet of Things (IoT)/Internet of Everything (IoE)envisioning connectivity of billions of devices. The URLLC requirementslike very low latency, very high reliability and variable mobility so onand so forth address the market segment representing the Industrialautomation application, vehicle-to-vehicle/vehicle-to-infrastructurecommunication foreseen as one of the enabler for autonomous cars.

In the fifth generation wireless communication system operating inhigher frequency (mmWave) bands, UE and gNB communicates with each otherusing Beamforming Beamforming techniques are used to mitigate thepropagation path losses and to increase the propagation distance forcommunication at higher frequency band. Beamforming enhances thetransmission and reception performance using a high-gain antenna.Beamforming can be classified into Transmission (TX) beamformingperformed in a transmitting end and reception (RX) beamforming performedin a receiving end. In general, the TX beamforming increases directivityby allowing an area in which propagation reaches to be densely locatedin a specific direction by using a plurality of antennas. In thissituation, aggregation of the plurality of antennas can be referred toas an antenna array, and each antenna included in the array can bereferred to as an array element. The antenna array can be configured invarious forms such as a linear array, a planar array, etc. The use ofthe TX beamforming results in the increase in the directivity of asignal, thereby increasing a propagation distance. Further, since thesignal is almost not transmitted in a direction other than a directivitydirection, a signal interference acting on another receiving end issignificantly decreased. The receiving end can perform beamforming on aRX signal by using a RX antenna array. The RX beamforming increases theRX signal strength transmitted in a specific direction by allowingpropagation to be concentrated in a specific direction, and excludes asignal transmitted in a direction other than the specific direction fromthe RX signal, thereby providing an effect of blocking an interferencesignal. By using beamforming technique, a transmitter can make pluralityof transmit beam patterns of different directions. Each of thesetransmit beam patterns can be also referred as transmit (TX) beam.Wireless communication system operating at high frequency uses pluralityof narrow TX beams to transmit signals in the cell as each narrow TXbeam provides coverage to a part of cell. The narrower the TX beam,higher is the antenna gain and hence the larger the propagation distanceof signal transmitted using beamforming A receiver can also makeplurality of receive (RX) beam patterns of different directions. Each ofthese receive patterns can be also referred as receive (RX) beam.

The fifth generation wireless communication system, supports standalonemode of operation as well dual connectivity (DC). In DC a multiple Rx/TxUE may be configured to utilize resources provided by two differentnodes (or NBs) connected via non-ideal backhaul. One node acts as theMaster Node (MN) and the other as the Secondary Node (SN). The MN and SNare connected via a network interface and at least the MN is connectedto the core network. NR also supports Multi-Radio Access Technology(RAT) Dual Connectivity (MR-DC) operation whereby a UE in radio resourcecontrol (RRC) CONNECTED is configured to utilize radio resourcesprovided by two distinct schedulers, located in two different nodesconnected via a non-ideal backhaul and providing eitherevolved-universal terrestrial radio access (E-UTRA) (i.e. if the node isan ng-eNB) or NR access (i.e. if the node is a gNB). In NR for a UE inRRC_CONNECTED not configured with carrier aggregation (CA)/DC there isonly one serving cell comprising of the primary cell. For a UE inRRC_CONNECTED configured with CA/DC the term ‘serving cells’ is used todenote the set of cells comprising of the Special Cell(s) and allsecondary cells (SCells). In NR the term Master Cell Group (MCG) refersto a group of serving cells associated with the Master Node, comprisingof the primary cell (PCell) and optionally one or more SCells. In NR theterm Secondary Cell Group (SCG) refers to a group of serving cellsassociated with the Secondary Node, comprising of the primary SCell(PSCell) and optionally one or more SCells. In NR PCell (primary cell)refers to a serving cell in MCG, operating on the primary frequency, inwhich the UE either performs the initial connection establishmentprocedure or initiates the connection re-establishment procedure. In NRfor a UE configured with CA, Scell is a cell providing additional radioresources on top of Special Cell. Primary SCG Cell (PSCell) refers to aserving cell in SCG in which the UE performs random access whenperforming the Reconfiguration with Sync procedure. For DualConnectivity operation the term SpCell (i.e. Special Cell) refers to thePCell of the MCG or the PSCell of the SCG, otherwise the term SpecialCell refers to the PCell.

In the fifth generation wireless communication system, Physical DownlinkControl Channel (PDCCH) is used to schedule downlink (DL) transmissionson physical downlink shared channel (PDSCH) and uplink (UL)transmissions on PUSCH, where the Downlink Control Information (DCI) onPDCCH includes: Downlink assignments containing at least modulation andcoding format, resource allocation, and hybrid-automatic repeat request(ARQ) information related to downlink scheduling (DL-SCH); Uplinkscheduling grants containing at least modulation and coding format,resource allocation, and hybrid-ARQ information related to uplinkscheduling (UL-SCH). In addition to scheduling, PDCCH can be used tofor: Activation and deactivation of configured PUSCH transmission withconfigured grant; Activation and deactivation of PDSCH semi-persistenttransmission; Notifying one or more UEs of the slot format; Notifyingone or more UEs of the physical resource blocks (PRB(s)) and orthogonalfrequency division multiplexing (OFDM) symbol(s) where the UE may assumeno transmission is intended for the UE; Transmission of transmit powercontrol (TPC) commands for physical uplink control channel (PUCCH) andPUSCH; Transmission of one or more TPC commands for sounding referencesignal (SRS) transmissions by one or more UEs; Switching a UE's activebandwidth part; Initiating a random access procedure. A UE monitors aset of PDCCH candidates in the configured monitoring occasions in one ormore configured COntrol REsource SETs (CORESETs) according to thecorresponding search space configurations. A CORESET consists of a setof PRBs with a time duration of 1 to 3 OFDM symbols. The resource unitsResource Element Groups (REGs) and Control Channel Elements (CCEs) aredefined within a CORESET with each CCE consisting a set of REGs. Controlchannels are formed by aggregation of CCE. Different code rates for thecontrol channels are realized by aggregating different number of CCE.Interleaved and non-interleaved CCE-to-REG mapping are supported in aCORESET. Polar coding is used for PDCCH. Each resource element groupcarrying PDCCH carries its own demodulation reference signal (DMRS).Quadrature phase-shift keying (QPSK) modulation is used for PDCCH.

In fifth generation wireless communication system, a list of searchspace configurations are signaled by gNB for each configured bandwidthpart (BWP) wherein each search configuration is uniquely identified byan identifier. Identifier of search space configuration to be used forspecific purpose such as paging reception, SI reception, random accessresponse reception is explicitly signaled by gNB. In NR search spaceconfiguration comprises of parameters Monitoring-periodicity-PDCCH-slot,Monitoring-offset-PDCCH-slot, Monitoring-symbols-PDCCH-within-slot andduration. A UE determines PDCCH monitoring occasion (s) within a slotusing the parameters PDCCH monitoring periodicity(Monitoring-periodicity-PDCCH-slot), the PDCCH monitoring offset(Monitoring-offset-PDCCH-slot), and the PDCCH monitoring pattern(Monitoring-symbols-PDCCH-within-slot). PDCCH monitoring occasions arethere in slots ‘x’ to x+duration where the slot with number ‘x’ in aradio frame with number ‘y’ satisfies the equation below:

(y*(number of slots in a radio frame)+x−Monitoring-offset-PDCCH-slot)mod (Monitoring-periodicity-PDCCH-slot)=0;

The starting symbol of a PDCCH monitoring occasion in each slot havingPDCCH monitoring occasion is given byMonitoring-symbols-PDCCH-within-slot. The length (in symbols) of a PDCCHmonitoring occasion is given in the corset associated with the searchspace. Search space configuration includes the identifier of CORESETconfiguration associated with it. A list of CORESET configurations aresignaled by gNB for each configured BWP wherein each CORESETconfiguration is uniquely identified by an identifier. Note that eachradio frame is of 10 ms duration. Radio frame is identified by a radioframe number or system frame number. Each radio frame comprises ofseveral slots wherein the number of slots in a radio frame and durationof slots depends on sub carrier spacing. The number of slots in a radioframe and duration of slots depends radio frame for each supported SCSis pre-defined in NR. Each CORESET configuration is associated with alist of transmission configuration indicator (TCI) states. One DL RS ID(synchronization signal block (SSB) or channel state informationreference signal (CSI RS)) is configured per TCI state. The list of TCIstates corresponding to a CORESET configuration is signaled by gNB viaRRC signaling. One of the TCI state in TCI state list is activated andindicated to UE by gNB. TCI state indicates the DL TX beam (DL TX beamis QCLed with SSB/CSI RS of TCI state) used by gNB for transmission ofPDCCH in the PDCCH monitoring occasions of a search space.

In fifth generation wireless communication system bandwidth adaptation(BA) is supported. With BA, the receive and transmit bandwidth of a UEneed not be as large as the bandwidth of the cell and can be adjusted:the width can be ordered to change (e.g. to shrink during period of lowactivity to save power); the location can move in the frequency domain(e.g. to increase scheduling flexibility); and the subcarrier spacingcan be ordered to change (e.g. to allow different services). A subset ofthe total cell bandwidth of a cell is referred to as a Bandwidth Part(BWP). BA is achieved by configuring RRC connected UE with BWP(s) andtelling the UE which of the configured BWPs is currently the active one.When BA is configured, the UE only has to monitor PDCCH on the oneactive BWP i.e. it does not have to monitor PDCCH on the entire DLfrequency of the serving cell. In RRC connected state, UE is configuredwith one or more DL and UL BWPs, for each configured Serving Cell (i.e.PCell or SCell). For an activated Serving Cell, there is always oneactive UL and DL BWP at any point in time. The BWP switching for aServing Cell is used to activate an inactive BWP and deactivate anactive BWP at a time. The BWP switching is controlled by the PDCCHindicating a downlink assignment or an uplink grant, by thebwp-InactivityTimer, by RRC signaling, or by the MAC entity itself uponinitiation of Random Access procedure. Upon addition of SpCell oractivation of an SCell, the DL BWP and UL BWP indicated byfirstActiveDownlinkBWP-Id and firstActiveUplinkBWP-Id respectively isactive without receiving PDCCH indicating a downlink assignment or anuplink grant. The active BWP for a Serving Cell is indicated by eitherRRC or PDCCH. For unpaired spectrum, a DL BWP is paired with a UL BWP,and BWP switching is common for both UL and DL. Upon expiry of BWPinactivity timer UE switch to the active DL BWP to the default DL BWP orinitial DL BWP (if default DL BWP is not configured).

In the 5G wireless communication system, random access (RA) issupported. Random access (RA) is used to achieve uplink (UL) timesynchronization. RA is used during initial access, handover, radioresource control (RRC) connection re-establishment procedure, schedulingrequest transmission, secondary cell group (SCG) addition/modification,beam failure recovery and data or control information transmission in ULby non-synchronized UE in RRC CONNECTED state. Several types of randomaccess procedure is supported.

Contention Based Random Access (CBRA)

This is also referred as 4 step CBRA. In this type of random access, UEfirst transmits Random Access preamble (also referred as Msg1) and thenwaits for Random access response (RAR) in the RAR window. RAR is alsoreferred as Msg2. Next generation node B (gNB) transmits the RAR onphysical downlink shared channel (PDSCH). PDCCH scheduling the PDSCHcarrying RAR is addressed to RA-radio network temporary identifier(RA-RNTI). RA-RNTI identifies the time-frequency resource (also referredas physical RA channel (PRACH) occasion or PRACH transmission (TX)occasion or RA channel (RACH) occasion) in which RA preamble wasdetected by gNB.

The RA-RNTI is calculated as follows:

RA-RNTI=1+s_id+14*t_id+14*80*f_id+14*80*8*ul_carrier_id,

where s_id is the index of the first orthogonal frequency divisionmultiplexing (OFDM) symbol of the PRACH occasion where UE hastransmitted Msg1, i.e. RA preamble; 0≤s_id<14; t_id is the index of thefirst slot of the PRACH occasion (0≤t_id<80); fid is the index of thePRACH occasion within the slot in the frequency domain (0≤f_id<8), andul_carrier_id is the UL carrier used for Msg1 transmission (0 for normalUL (NUL) carrier and 1 for supplementary UL (SUL) carrier.

Several RARs for various Random access preambles detected by gNB can bemultiplexed in the same RAR media access control (MAC) protocol dataunit (PDU) by gNB. An RAR in MAC PDU corresponds to UE's RA preambletransmission if the RAR includes an RA preamble identifier (RAPID) of RApreamble transmitted by the UE. If the RAR corresponding to its RApreamble transmission is not received during the RAR window and UE hasnot yet transmitted the RA preamble for a configurable (configured bygNB in RACH configuration) number of times, the UE goes back to firststep i.e. select random access resource (preamble/RACH occasion) andtransmits the RA preamble. A backoff may be applied before going back tofirst step.

If the RAR corresponding to its RA preamble transmission is received theUE transmits message 3 (Msg3) in UL grant received in RAR. Msg3 includesmessage such as RRC connection request, RRC connection re-establishmentrequest, RRC handover confirm, scheduling request, SI request etc. Itmay include the UE identity (i.e. cell-radio network temporaryidentifier (C-RNTI) or system architecture evolution (SAE)-temporarymobile subscriber identity (S-TMSI) or a random number). Aftertransmitting the Msg3, UE starts a contention resolution timer. Whilethe contention resolution timer is running, if UE receives a physicaldownlink control channel (PDCCH) addressed to C-RNTI included in Msg3,contention resolution is considered successful, contention resolutiontimer is stopped and RA procedure is completed. While the contentionresolution timer is running, if UE receives contention resolution MACcontrol element (CE) including the UE's contention resolution identity(first X bits of common control channel (CCCH) service data unit (SDU)transmitted in Msg3), contention resolution is considered successful,contention resolution timer is stopped and RA procedure is completed. Ifthe contention resolution timer expires and UE has not yet transmittedthe RA preamble for a configurable number of times, UE goes back tofirst step i.e. select random access resource (preamble/RACH occasion)and transmits the RA preamble. A backoff may be applied before goingback to first step.

Contention Free Random Access (CFRA)

This is also referred as legacy CFRA or 4 step CFRA. CFRA procedure isused for scenarios such as handover where low latency is required,timing advance establishment for secondary cell (Scell), etc. Evolvednode B (eNB) assigns to UE dedicated Random access preamble. UEtransmits the dedicated RA preamble. ENB transmits the RAR on PDSCHaddressed to RA-RNTI. RAR conveys RA preamble identifier and timingalignment information. RAR may also include UL grant. RAR is transmittedin RAR window similar to contention based RA (CBRA) procedure. CFRA isconsidered successfully completed after receiving the RAR including RApreamble identifier (RAPID) of RA preamble transmitted by the UE. Incase RA is initiated for beam failure recovery, CFRA is consideredsuccessfully completed if PDCCH addressed to C-RNTI is received insearch space for beam failure recovery. If the RAR window expires and RAis not successfully completed and UE has not yet transmitted the RApreamble for a configurable (configured by gNB in RACH configuration)number of times, the UE retransmits the RA preamble.

For certain events such has handover and beam failure recovery ifdedicated preamble(s) are assigned to UE, during first step of randomaccess i.e. during random access resource selection for Msg1transmission UE determines whether to transmit dedicated preamble or nondedicated preamble. Dedicated preambles are typically provided for asubset of SSBs/CSI RSs. If there is no SSB/CSI RS having DL RSRP above athreshold amongst the SSBs/CSI RSs for which contention free randomaccess resources (i.e. dedicated preambles/ROs) are provided by gNB, UEselect non dedicated preamble. Otherwise UE select dedicated preamble.So, during the RA procedure, one random access attempt can be CFRA whileother random access attempt can be CBRA.

2 Step Contention Based Random Access (2 Step CBRA)

In the first step, UE transmits random access preamble on PRACH and apayload (i.e. MAC PDU) on PUSCH. The random access preamble and payloadtransmission is also referred as MsgA. In the second step, after MsgAtransmission, the UE monitors for a response from the network (i.e. gNB)within a configured window. The response is also referred as MsgB. IfCCCH SDU was transmitted in MsgA payload, UE performs contentionresolution using the contention resolution information in MsgB. Thecontention resolution is successful if the contention resolutionidentity received in MsgB matches first 48 bits of CCCH SDU transmittedin MsgA. If C-RNTI was transmitted in MsgA payload, the contentionresolution is successful if UE receives PDCCH addressed to C-RNTI. Ifcontention resolution is successful, random access procedure isconsidered successfully completed. Instead of contention resolutioninformation corresponding to the transmitted MsgA, MsgB may include afallback information corresponding to the random access preambletransmitted in MsgA. If the fallback information is received, UEtransmits Msg3 and performs contention resolution using Msg4 as in CBRAprocedure. If contention resolution is successful, random accessprocedure is considered successfully completed. If contention resolutionfails upon fallback (i.e. upon transmitting Msg3), UE retransmits MsgA.If configured window in which UE monitor network response aftertransmitting MsgA expires and UE has not received MsgB includingcontention resolution information or fallback information as explainedabove, UE retransmits MsgA. If the random access procedure is notsuccessfully completed even after transmitting the msgA configurablenumber of times, UE fallbacks to 4 step RACH procedure i.e. UE onlytransmits the PRACH preamble.

MsgA payload may include one or more of common control channel (CCCH)service data unit (SDU), dedicated control channel (DCCH) SDU, dedicatedtraffic channel (DTCH) SDU, buffer status report (BSR) MAC controlelement (CE), power headroom report (PHR) MAC CE, SSB information,C-RNTI MAC CE, or padding. MsgA may include UE ID (e.g. random ID,S-TMSI, C-RNTI, resume ID, etc.) along with preamble in first step. TheUE ID may be included in the MAC PDU of the MsgA. UE ID such as C-RNTImay be carried in MAC CE wherein MAC CE is included in MAC PDU. Other UEIDs (such random ID, S-TMSI, C-RNTI, resume ID, etc.) may be carried inCCCH SDU. The UE ID can be one of random ID, S-TMSI, C-RNTI, resume ID,IMSI, idle mode ID, inactive mode ID, etc. The UE ID can be different indifferent scenarios in which UE performs the RA procedure. When UEperforms RA after power on (before it is attached to the network), thenUE ID is the random ID. When UE perform RA in IDLE state after it isattached to network, the UE ID is S-TMSI. If UE has an assigned C-RNTI(e.g. in connected state), the UE ID is C-RNTI. In case UE is inINACTIVE state, UE ID is resume ID. In addition to UE ID, some additionctrl information can be sent in MsgA. The control information may beincluded in the MAC PDU of the MsgA. The control information may includeone or more of connection request indication, connection resume requestindication, SI request indication, buffer status indication, beaminformation (e.g. one or more DL TX beam ID(s) or SSB ID(s)), beamfailure recovery indication/information, data indicator,cell/BS/transmission/reception point (TRP) switching indication,connection re-establishment indication, reconfiguration complete orhandover complete message, etc.

2 Step Contention Free Random Access (2 Step CFRA)

In this case gNB assigns to UE dedicated Random access preamble (s) andPUSCH resource(s) for MsgA transmission. RO(s) to be used for preambletransmission may also be indicated. In the first step, UE transmitsrandom access preamble on PRACH and a payload on PUSCH using thecontention free random access resources (i.e. dedicated preamble/PUSCHresource/RO). In the second step, after MsgA transmission, the UEmonitors for a response from the network (i.e. gNB) within a configuredwindow. If UE receives PDCCH addressed to C-RNTI, random accessprocedure is considered successfully completed. If UE receives fallbackinformation corresponding to its transmitted preamble, random accessprocedure is considered successfully completed.

For certain events such has handover and beam failure recovery ifdedicated preamble(s) and PUSCH resource(s) are assigned to UE, duringfirst step of random access i.e. during random access resource selectionfor MsgA transmission UE determines whether to transmit dedicatedpreamble or non dedicated preamble. Dedicated preambles are typicallyprovided for a subset of SSBs/CSI RSs. If there is no SSB/CSI RS havingDL RSRP above a threshold amongst the SSBs/CSI RSs for which contentionfree random access resources (i.e. dedicated preambles/ROs/PUSCHresources) are provided by gNB, UE select non dedicated preamble.Otherwise UE select dedicated preamble. So, during the RA procedure, onerandom access attempt can be 2 step CFRA while other random accessattempt can be 2 step CBRA.

Upon initiation of random access procedure, UE first selects the carrier(SUL or NUL). If the carrier to use for the random access procedure isexplicitly signaled by gNB, UE select the signaled carrier forperforming Random Access procedure. If the carrier to use for the RandomAccess procedure is not explicitly signaled by gNB; and if the ServingCell for the Random Access procedure is configured with supplementaryuplink and if the RSRP of the downlink pathloss reference is less thanrsrp-ThresholdSSB-SUL: UE select the SUL carrier for performing RandomAccess procedure. Otherwise, UE select the NUL carrier for performingRandom Access procedure. Upon selecting the UL carrier, UE determinesthe UL and DL BWP for random access procedure as specified in section5.15 of TS 38.321. UE then determines whether to perform 2 step or 4step RACH for this random access procedure.

-   -   If this random access procedure is initiated by PDCCH order and        if the ra-PreambleIndex explicitly provided by PDCCH is not        0b000000, UE selects 4 step RACH.    -   else if 2 step contention free random access resources are        signaled by gNB for this random access procedure, UE selects 2        step RACH.    -   else if 4 step contention free random access resources are        signaled by gNB for this random access procedure, UE selects 4        step RACH.    -   else if the UL BWP selected for this random access procedure is        configured with only 2 step RACH resources, UE selects 2 step        RACH.    -   else if the UL BWP selected for this random access procedure is        configured with only 4 step RACH resources, UE selects 4 step        RACH.    -   else if the UL BWP selected for this random access procedure is        configured with both 2 step and 4 step RACH resources,    -   if RSRP of the downlink pathloss reference is below a configured        threshold, UE selects 4 step RACH. Otherwise UE selects 2 step        RACH.

In the fifth generation wireless communication system, node B (gNB) orbase station in cell broadcast Synchronization Signal and PBCH block(SSB) consists of primary and secondary synchronization signals (PSS,SSS) and system information. System information includes commonparameters needed to communicate in cell. In the fifth generationwireless communication system (also referred as next generation radio orNR), System Information (SI) is divided into the master informationblock (MIB) and a number of SIBs where:

the MIB is always transmitted on the BCH with a periodicity of 80 ms andrepetitions made within 80 ms and it includes parameters that are neededto acquire SIB1 from the cell.

the SIB1 is transmitted on the DL-SCH with a periodicity of 160 ms andvariable transmission repetition. The default transmission repetitionperiodicity of SIB1 is 20 ms but the actual transmission repetitionperiodicity is up to network implementation. The scheduling informationin SIB 1 includes mapping between SIBs and SI messages, periodicity ofeach SI message and SI window length. The scheduling information in SIB1 includes an indicator for each SI message, which indicates whether theconcerned SI message is being broadcasted or not. If at least one SImessage is not being broadcasted, SIB1 may include random accessresources (PRACH preamble(s) and PRACH resource(s)) for requesting gNBto broadcast one or more SI message(s).

SIBs other than SIB1 are carried in SystemInformation (SI) messages,which are transmitted on the DL-SCH. Only SIBs having the sameperiodicity can be mapped to the same SI message. Each SI message istransmitted within periodically occurring time domain windows (referredto as SI-windows with same length for all SI messages). Each SI messageis associated with a SI-window and the SI-windows of different SImessages do not overlap. That is, within one SI-window only thecorresponding SI message is transmitted. Any SIB except SIB 1 can beconfigured to be cell specific or area specific, using an indication inSIB 1. The cell specific SIB is applicable only within a cell thatprovides the SIB while the area specific SIB is applicable within anarea referred to as SI area, which consists of one or several cells andis identified by systemInformationAreaID.

UE acquires SIB 1 from the camped or serving cell. UE check theBroadcastStatus bit in SIB 1 for SI message which UE needs to acquire.SI request configuration for SUL is signalled by gNB using the IEsi-RequestConfigSUL in SIB 1. If the IE si-RequestConfigSUL is notpresent in SIB 1, UE considers that SI request configuration for SUL isnot signalled by gNB. SI request configuration for NUL is signalled bygNB using the IE si-RequestConfig in SIB 1. If the IE si-RequestConfigis not present in SIB1, UE considers that SI request configuration forNUL is not signalled by gNB. If SI message which UE needs to acquire isnot being broadcasted (i.e. BroadcastStatus bit is set to zero), UEinitiates transmission of SI request. The procedure for SI requesttransmission is as follows:

If SI request configuration is signaled by gNB for SUL, and criteria toselect SUL is met (i.e. RSRP derived from SSB measurements of camped orserving cell <rsrp-ThresholdSSB-SUL, where rsrp-ThresholdSSB-SUL issignaled by gNB (e.g. in broadcast signaling such as SIB 1)): UEinitiate transmission of SI request based on Msg1 based SI request onSUL. In other words, UE initiates Random Access procedure using thePRACH preamble(s) and PRACH resource(s) in SI request configuration ofSUL. UE transmits Msg1 (i.e. Random access preamble) and waits foracknowledgement for SI request. Random access resources (PRACHpreamble(s) and PRACH occasions(s)) indicated in SI requestconfiguration of SUL is used for Msg1. Msg1 is transmitted on SUL. Ifacknowledgement for SI request is received, UE monitors the SI window ofthe requested SI message in one or more SI period(s) of that SI message.

Else if SI request configuration is signaled by gNB for NUL and criteriato select NUL is met (i.e. NUL is selected if SUL is supported in campedor serving cell and RSRP derived from SSB measurements of camped orserving cell >=rsrp-ThresholdSSB-SUL; OR NUL is selected if SUL is notsupported in serving cell): UE initiate transmission of SI request basedon Msg1 based SI request on NUL (350). In other words, UE initiatesRandom Access procedure using the PRACH preamble(s) and PRACHresource(s) in SI request configuration of NUL. UE transmits Msg1 (i.e.Random access preamble) and waits for acknowledgement for SI request.Random access resources (PRACH preamble(s) and PRACH occasions(s))indicated in SI request configuration of NUL is used for Msg1. Msg1 istransmitted on NUL. If acknowledgement for SI request is received, UEmonitors the SI window of the requested SI message in one or more SIperiod(s) of that SI message.

Else UE initiate transmission of SI request based on Msg3 based SIrequest. In other words, UE initiate transmission ofRRCSystemInfoRequest message (345). UE transmits Msg1 (i.e. Randomaccess preamble) and waits for random access response. Common randomaccess resources (PRACH preamble(s) and PRACH occasions(s)) are used forMsg1. In the UL grant received in random access response, UE transmitsRRCSystemInfoRequest message and waits for acknowledgement for SIrequest (i.e. RRCSystemInfoRequest message). If acknowledgement for SIrequest (i.e. RRCSystemInfoRequest message) is received, UE monitors theSI window of the requested SI message in one or more SI period(s) ofthat SI message. Note that if SUL is configured, UL carrier for Msg1transmission will be selected by UE in similar manner as selected by UEfor Msg1 based SI request. SUL is the selected UL carrier, if RSRPderived from SSB measurements of camped or serving cell<rsrp-ThresholdSSB-SUL where rsrp-ThresholdSSB-SUL is signaled by gNB(e.g. in broadcast signaling such as SIB1). NUL is the selected ULcarrier, if RSRP derived from SSB measurements of camped or servingcell >=rsrp-ThresholdSSB-SUL where rsrp-ThresholdSSB-SUL is signaled bygNB (e.g. in broadcast signaling such as SIB1).

4G wireless communication system supports early data transmission (EDT).EDT allows one uplink data transmission optionally followed by onedownlink data transmission during the random access procedure. EDT istriggered when the upper layers have requested the establishment orresumption of the RRC Connection for Mobile Originated data (i.e., notsignaling or SMS) and the uplink data size is less than or equal to a TBsize indicated in the system information.

FIG. 1 shows an operation for explaining an example of early datatransmission (EDT) according to an embodiment of the disclosure.

Referring to FIG. 1, in one approach of EDT, uplink user data aretransmitted in a NAS message concatenated in UL RRCEarlyDataRequestmessage on CCCH. Downlink user data are optionally transmitted in a NASmessage concatenated in DL RRCEarlyDataComplete message on CCCH. Thereis no transition to RRC CONNECTED. The detailed procedure (see FIG. 1)is as follows:

Steps 111-113. Upon connection establishment request for MobileOriginated data from the upper layers, the UE (101) initiates the earlydata transmission procedure and selects a random access preambleconfigured for EDT.

Step 115. UE sends RRCEarlyDataRequest message concatenating the userdata on CCCH.

Step 117. The eNB (103) initiates the S1-AP Initial UE message procedureto forward the NAS message and establish the S1 connection. The eNB mayindicate in this procedure that this connection is triggered for EDT.

Step 119. The MME (105) requests the S-GW (107) to re-activate the EPSbearers for the UE.

Step 121. The MME sends the uplink data to the S-GW.

Step 123. If downlink data are available, the S-GW sends the downlinkdata to the MME.

Steps 125 a-125 b. If downlink data are received from the S-GW, the MMEforwards the data to the eNB via DL NAS Transport procedure and may alsoindicate whether further data are expected. Otherwise, the MME maytrigger Connection Establishment Indication procedure and also indicatewhether further data are expected.

Step 127. If no further data are expected, the eNB can send theRRCEarlyDataComplete message on CCCH to keep the UE in RRC IDLE. Ifdownlink data were received in step 6, they are concatenated inRRCEarlyDataComplete message.

Steps 129-131. The S1 connection is released and the EPS bearers aredeactivated.

NOTE: If the MME or the eNB decides to move the UE in RRC_CONNECTEDmode, RRCConnectionSetup message is sent in step 7 to fall back to thelegacy RRC Connection establishment procedure; the eNB will discard thezero-length NAS PDU received in msg5.

FIG. 2 shows an operation for explaining another example of EDTaccording to an embodiment of the disclosure.

Referring to FIG. 2, in another approach of EDT, the UE has beenprovided with a NextHopChainingCount in the RRCConnectionRelease messagewith suspend indication. Uplink user data are transmitted on DTCHmultiplexed with UL RRCConnectionResumeRequest message on CCCH. Downlinkuser data are optionally transmitted on DTCH multiplexed with DLRRCConnectionRelease message on DCCH. The short resume MAC-I is reusedas the authentication token for RRCConnectionResumeRequest message andis calculated using the integrity key from the previous connection. Theuser data in uplink and downlink are ciphered. The keys are derivedusing the NextHopChainingCount provided in the RRCConnectionReleasemessage of the previous RRC connection. The RRCConnectionRelease messageis integrity protected and ciphered using the newly derived keys. Thereis no transition to RRC CONNECTED. The detailed procedure (see FIG. 2)is as follows:

Steps 211-213. Upon connection resumption request for Mobile Originateddata from the upper layers, the UE (201) initiates the early datatransmission procedure and selects a random access preamble configuredfor EDT.

Step 215. The UE sends an RRCConnectionResumeRequest to the eNB (203),including its Resume ID, the establishment cause, and an authenticationtoken. The UE resumes all SRBs and DRBs, derives new security keys usingthe NextHopChainingCount provided in the RRCConnectionRelease message ofthe previous connection and re-establishes the AS security. The userdata are ciphered and transmitted on DTCH multiplexed with theRRCConnectionResumeRequest message on CCCH.

Step 217. The eNB initiates the S1-AP Context Resume procedure to resumethe S1 connection and re-activate the S1-U bearers.

Step 219. The MME (205) requests the S-GW (207) to re-activate the S1-Ubearers for the UE.

Step 221. The MME confirms the UE context resumption to the eNB.

Step 223. The uplink data are delivered to the S-GW.

Steps 225. If downlink data are available, the S-GW sends the downlinkdata to the eNB.

Steps 227-229. If no further data are expected from the S-GW, the eNBcan initiate the suspension of the S1 connection and the deactivation ofthe S1-U bearers.

Step 231. The eNB sends the RRCConnectionRelease message to keep the UEin RRC IDLE. The message includes the releaseCause set to rrc-Suspend,the resumeID, the NextHopChainingCount and drb-ContinueROHC which arestored by the UE. If downlink data were received in step 6, they aresent ciphered on DTCH multiplexed with the RRCConnectionRelease messageon DCCH.

NOTE: If the MME or eNB decides the UE to move in RRC_CONNECTED mode,RRCConnectionResume message is sent in step 7 to fall back to the RRCConnection resume procedure. In that case, the RRCConnectionResumemessage is integrity protected and ciphered with the keys derived instep 1 and the UE ignores the NextHopChainingCount included in theRRCConnectionResume message. Downlink data can be transmitted on DTCHmultiplexed with the RRCConnectionResume message.

4G and 5G wireless communication system supports vehicular communicationservices. Vehicular communication services, represented byvehicle-to-everything (V2X) services, can consist of the following fourdifferent types: V2V, V2I, V2N and V2P. In fifth generation (alsoreferred as NR or New Radio) wireless communication system, V2Xcommunication is being enhanced to support enhanced V2X use cases, whichare broadly arranged into four use case groups:

1) Vehicles Platooning enables the vehicles to dynamically form aplatoon travelling together. All the vehicles in the platoon obtaininformation from the leading vehicle to manage this platoon. Theseinformation allow the vehicles to drive closer than normal in acoordinated manner, going to the same direction and travelling together.

2) Extended Sensors enables the exchange of raw or processed datagathered through local sensors or live video images among vehicles, roadsite units, devices of pedestrian and V2X application servers. Thevehicles can increase the perception of their environment beyond of whattheir own sensors can detect and have a more broad and holistic view ofthe local situation. High data rate is one of the key characteristics.

3) Advanced Driving enables semi-automated or full-automated driving.Each vehicle and/or RSU shares its own perception data obtained from itslocal sensors with vehicles in proximity and that allows vehicles tosynchronize and coordinate their trajectories or maneuvers. Each vehicleshares its driving intention with vehicles in proximity too.

4) Remote Driving enables a remote driver or a V2X application tooperate a remote vehicle for those passengers who cannot drive bythemselves or remote vehicles located in dangerous environments. For acase where variation is limited and routes are predictable, such aspublic transportation, driving based on cloud computing can be used.High reliability and low latency are the main requirements.

FIG. 3 illustrates NG-RAN architecture supporting PC5 interfaceaccording to an embodiment of the disclosure.

Referring to FIG. 3, V2X services can be provided by PC5 interfaceand/or Uu interface. Support of V2X services via PC5 interface isprovided by NR sidelink communication or V2X sidelink communication,which is a mode of communication whereby UEs can communicate with eachother directly over the PC5 interface using NR technology or EUTRAtechnology respectively without traversing any network node. Thiscommunication mode is supported when the UE is served by RAN and whenthe UE is outside of RAN coverage. Only the UEs authorized to be usedfor V2X services can perform NR or V2X sidelink communication. TheNG-RAN architecture supports the PC5 interface as illustrated in FIG. 3.Sidelink transmission and reception over the PC5 interface are supportedwhen the UE is inside NG-RAN coverage, irrespective of which RRC statethe UE is in, and when the UE is outside NG-RAN coverage. Support of V2Xservices via the PC5 interface can be provided by NR SidelinkCommunication and/or V2X Sidelink Communication. NR SidelinkCommunication may be used to support other services than V2X services.

NR or V2X Sidelink Communication can support three types of transmissionmodes. Unicast transmission, characterized by support of at least onePC5-RRC connection between peer UEs; Transmission and reception ofcontrol information and user traffic between peer UEs in sidelink;Support of sidelink HARQ feedback; Support of RLC AM; and Support ofsidelink RLM for both peer UEs to detect RLF. Groupcast transmission,characterized by: Transmission and reception of user traffic among UEsbelonging to a group in sidelink; Support of sidelink HARQ feedback.Broadcast transmission, characterized by: Transmission and reception ofuser traffic among UEs in sidelink.

The AS protocol stack for the control plane in the PC5 interfaceconsists of RRC, packet data convergence protocol (PDCP), RLC and MACsublayer, and the physical layer. The AS protocol stack for user planein the PC5 interface consists of SDAP, PDCP, RLC and MAC sublayer, andthe physical layer. Sidelink Radio bearers (SLRB) are categorized intotwo groups: sidelink data radio bearers (SL DRB) for user plane data andsidelink signaling radio bearers (SL SRB) for control plane data.Separate SL SRBs using different SCCHs are configured for PC5-RRC andPC5-S signaling respectively.

The MAC sublayer provides the following services and functions over thePC5 interface:—Radio resource selection; Packet filtering; Priorityhandling between uplink and sidelink transmissions for a given UE;Sidelink CSI reporting. With LCP restrictions in MAC, only sidelinklogical channels belonging to the same destination can be multiplexedinto a MAC PDU for every unicast, groupcast and broadcast transmissionwhich is associated to the destination. NG-RAN can also control whethera sidelink logical channel can utilize the resources allocated to aconfigured sidelink grant Type 1. For packet filtering, a SL-SCH MACheader including portions of both Source Layer-2 ID and a DestinationLayer-2 ID is added to each MAC PDU as specified in subclause 8.x.Logical Channel Identifier (LCID) included within a MAC subheaderuniquely identifies a logical channel within the scope of the SourceLayer-2 ID and Destination Layer-2 ID combination. The following logicalchannels are used in sidelink:

-   -   Sidelink Control Channel (SCCH): a sidelink channel for        transmitting control information from one UE to other UE(s);    -   Sidelink Traffic Channel (STCH): a sidelink channel for        transmitting user information from one UE to other UE(s);    -   Sidelink Broadcast Control Channel (SBCCH): a sidelink channel        for broadcasting sidelink system information from one UE to        other UE(s).

The following connections between logical channels and transportchannels exist:

-   -   SCCH can be mapped to SL-SCH;    -   STCH can be mapped to SL-SCH;    -   SBCCH can be mapped to SL-BCH.

The RRC sublayer provides the following services and functions over thePC5 interface:

-   -   Transfer of a PC5-RRC message between peer UEs;    -   Maintenance and release of a PC5-RRC connection between two UEs;    -   Detection of sidelink radio link failure for a PC5-RRC        connection.

A PC5-RRC connection is a logical connection between two UEs for a pairof Source and Destination Layer-2 IDs which is considered to beestablished after a corresponding PC5 unicast link is established asspecified in TS 23.287. There is one-to-one correspondence between thePC5-RRC connection and the PC5 unicast link. A UE may have multiplePC5-RRC connections with one or more UEs for different pairs of Sourceand Destination Layer-2 IDs. Separate PC5-RRC procedures and messagesare used for a UE to transfer UE capability and sidelink configurationincluding SLRB configuration to the peer UE. Both peer UEs can exchangetheir own UE capability and sidelink configuration using separatebi-directional procedures in both sidelink directions. If it is notinterested in sidelink transmission, if sidelink RLF on the PC5-RRCconnection is declared, or if the Layer-2 link release procedure iscompleted as specified in TS 23.287, UE releases the PC5-RRC connection.

The UE can operate in two modes for resource allocation in sidelink:

-   -   Scheduled resource allocation, characterized by:    -   The UE needs to be RRC_CONNECTED in order to transmit data;    -   NG-RAN schedules transmission resources.    -   UE autonomous resource selection, characterized by:    -   The UE can transmit data when inside NG-RAN coverage,        irrespective of which RRC state the UE is in, and when outside        NG-RAN coverage;    -   The UE autonomously selects transmission resources from a pool        of resources.

For NR sidelink communication, the UE performs sidelink transmissionsonly on a single carrier.

Scheduled Resource Allocation

NG-RAN can dynamically allocate resources to the UE via the SL-RNTI onPDCCH(s) for NR sidelink Communication. In addition, NG-RAN can allocatesidelink resources to UE with two types of configured sidelink grants:

With type 1, RRC directly provides the configured sidelink grant for NRsidelink communication

With type 2, RRC provides the periodicity of the configured sidelinkgrant while PDCCH can either signal and activate the configured sidelinkgrant, or deactivate it. The PDCCH provides the actual grant (i.e.resources) to be used. The PDCCH is addressed to SL-CS-RNTI for NRsidelink communication and SL Semi-Persistent Scheduling V-RNTI for V2Xsidelink communication.

For the UE performing NR sidelink communication, there can be more thanone configured sidelink grant activated at a time on the carrierconfigured for sidelink transmission. When beam failure or physicallayer problem occurs on NR Uu, the UE can continue using the configuredsidelink grant Type 1. During handover, the UE can be provided withconfigured sidelink grants via handover command, regardless of the type.If provided, the UE activates the configured sidelink grant Type 1 uponreception of the handover command. The UE can send sidelink bufferstatus report to support scheduler operation in NG-RAN. The sidelinkbuffer status reports refer to the data that is buffered in for a groupof logical channels (LCG) per destination in the UE. Eight LCGs are usedfor reporting of the sidelink buffer status reports. Two formats, whichare SL BSR and truncated SL BSR, are used.

UE sends SL BSR for dynamic resource allocation, in following cases:

SL data, for a sidelink logical channel of a ProSe Destination, becomesavailable for transmission in the RLC entity or in the PDCP entity andeither the data belongs to a sidelink logical channel with higherpriority than the priorities of the sidelink logical channels whichbelong to any LCG belonging to the same ProSe Destination and for whichdata is already available for transmission, or there is currently nodata available for transmission for any of the sidelink logical channelsbelonging to the same ProSe Destination, in which case the Sidelink BSRis referred below to as “Regular Sidelink BSR”;

UL resources are allocated and number of padding bits remaining after aPadding BSR has been triggered is equal to or larger than the size ofthe Sidelink BSR MAC control element containing the buffer status for atleast one LCG of a ProSe Destination plus its subheader, in which casethe Sidelink BSR is referred below to as “Padding Sidelink BSR”;

retx-BSR-TimerSL expires and the MAC entity has data available fortransmission for any of the sidelink logical channels, in which case theSidelink BSR is referred below to as “Regular Sidelink BSR”;

periodic-BSR-TimerSL expires, in which case the Sidelink BSR is referredbelow to as “Periodic Sidelink BSR”.

UE Autonomous Resource Allocation

The UE autonomously selects sidelink grant from a pool of resourcesprovided by broadcast system information or dedicated signaling whileinside NG-RAN coverage or by preconfiguration while outside NG-RANcoverage.

For NR sidelink communication, the pools of resources can be providedfor a given validity area where the UE does not need to acquire a newpool of resources while moving within the validity area, at least whenthis pool is provided by SIB (e.g. reuse valid area of NR SIB). NR SIBvalidity mechanism is reused to enable validity area for SL resourcepool configured via broadcasted system information. The UE is allowed totemporarily use UE autonomous resource selection with random selectionfor sidelink transmission based on configuration of the exceptionaltransmission resource pool.

For V2X sidelink transmission, during handover, transmission resourcepool configurations including exceptional transmission resource pool forthe target cell can be signaled in the handover command to reduce thetransmission interruption. In this way, the UE may use the V2X sidelinktransmission resource pools of the target cell before the handover iscompleted as long as either synchronization is performed with the targetcell in case eNB is configured as synchronization source orsynchronization is performed with global navigation satellite system(GNSS) in case GNSS is configured as synchronization source. If theexceptional transmission resource pool is included in the handovercommand, the UE uses randomly selected resources from the exceptionaltransmission resource pool, starting from the reception of handovercommand. If the UE is configured with scheduled resource allocation inthe handover command, the UE continues to use the exceptionaltransmission resource pool while the timer associated with handover isrunning. If the UE is configured with autonomous resource selection inthe target cell the UE continues to use the exceptional transmissionresource pool until the sensing results on the transmission resourcepools for autonomous resource selection are available. For exceptionalcases (e.g. during RLF, during transition from RRC IDLE to RRC CONNECTEDor during change of dedicated V2X sidelink resource pools within acell), the UE may select resources in the exceptional pool provided inserving cell's SIB21 or in dedicated signaling based on randomselection, and uses them temporarily. During cell reselection, the RRCIDLE UE may use the randomly selected resources from the exceptionaltransmission resource pool of the reselected cell until the sensingresults on the transmission resource pools for autonomous resourceselection are available.

UE can be configured with both scheduled resource allocation (i.e. Mode1 or M1) and autonomous resource allocation (i.e. Mode 2 or M2)scheduling modes. gNB indicates scheduling mode (Mode 1 or Mode 2)associated with each SL LCH. Based on NW/UE trigger scheduling mode maybe changed for one or more logical channels. In case scheduling mode ischanged, it is proposed to trigger SL BSR. However, triggering SL BSRwhenever mode changes leads to unnecessary overhead.

Scheduling Mode is Changed from M2 to M1 for One or More SL LCH(s)

It is noted that the methods disclosed in this embodiment are alsoapplicable for the case when scheduling mode is changed from M2 to M1+M2for one or more SL LCH(s).

Method 1

gNB signals scheduling mode (M1 or M2 or both) associated with each SLLCH. The signaling can be via RRC message. Later scheduling modeassociated with one or more SL LCHs is changed by gNB wherein the gNBsends RRC signaling message (or another signaling method such as MAC CE)with updated association between SL LCH(s) and scheduling modes.Scheduling mode associated with one or more SL LCHs can also be changedby UE when criteria to change mode is met. The criteria can be based onSL quality or Channel Busy Ratio (CBR) measurement of SL resources, etc.

FIG. 4 illustrates an embodiment of UE operation when scheduling mode ischanged from M2 to M1 for one or more SL LCHs according to an embodimentof the disclosure.

Referring to FIG. 4, UE operation when scheduling mode is changed fromM2 (i.e. UE autonomous Resource Allocation) to M1 (i.e. ScheduledResource Allocation) for one or more SL LCHs at operation 400 is asfollows:

In an embodiment of this method, if SL data (i.e. packets or RLC SDUs)is available for transmission in the RLC entity of SL LCH for which modeis changed from M2 to M1 at operation 405, UE (i.e. MAC entity in UE)triggers SL BSR (step 410). If not, UE does not trigger SL BSR atoperation 415. Note that if this condition is met for multiple SL LCHs,only one SL BSR is triggered.

In another embodiment of this method, if SL data (i.e. packets or PDCPSDUs) is available for transmission in the PDCP entity of SL LCH forwhich mode is changed from M2 to M1 at operation 405, UE (i.e. MACentity in UE) triggers SL BSR at operation 410. If not, UE does nottrigger SL BSR at operation 415. Note that if this condition is met formultiple SL LCHs, only one SL BSR is triggered.

In another embodiment of this method, if SL data for a logical channel(of a destination) for which mode is changed from M2 to M1 and whichbelongs to an LCG, becomes available to the MAC entity at operation 405,UE (i.e. MAC entity in UE) triggers SL BSR (step 410). If not, UE doesnot trigger SL BSR at operation 415. Note that if this condition is metfor multiple SL LCHs, only one SL BSR is triggered.

In another embodiment of this method, if SL data for a SL LCH of adestination for which mode is changed from M2 to M1, becomes availableto the MAC entity at operation 410, UE (i.e. MAC entity in UE) triggersSL BSR at operation 410. If not, UE does not trigger SL BSR at operation415. Note that if this condition is met for multiple SL LCHs, only oneSL BSR is triggered.

For the triggered SL BSR, UE includes SL BSR MAC CE in MAC PDU andtransmit it to the gNB using UL SCH resource. If UL SCH resource is notavailable or if UL SCH resource is available but the SL BSR MAC CEcannot be accommodated in the UL SCH resource, UE may also triggerscheduling request wherein scheduling request is sent to gNB using PUCCHresource.

In an embodiment, triggered SL BSR is a regular SL BSR. SL BSR MAC CEfor SL BSR includes data volume for one or more LCGs wherein for eachreported LCG, ‘buffer size, LCG ID and destination index’ is included inSL BSR.

In another embodiment, triggered SL BSR is a truncated SL BSR whereindata volume of LCG(s) associated with SL LCH(s) for which mode ischanged is reported. SL BSR MAC CE for truncated SL BSR includes datavolume for one or more LCGs wherein for each reported LCG, ‘buffer size,LCG ID and destination index’ is included in truncated SL BSR.

In another embodiment, triggered SL BSR is a truncated SL BSR whereindata volume of LCG(s) associated with SL LCH(s) for which ‘mode ischanged and SL data is available for transmission’ is reported. SL BSRMAC CE for truncated SL BSR includes data volume for one or more LCGswherein for each reported LCG, ‘buffer size, LCG ID and destinationindex’ is included in truncated SL BSR.

In another embodiment, triggered SL BSR is a special SL BSR wherein datavolume of LCG(s) associated with SL LCH(s) for which mode is changed isreported. SL BSR MAC CE for special SL BSR includes data volume for oneor more LCGs wherein for each reported LCG, ‘buffer size, LCG ID anddestination index’ is included in special SL BSR. LCID in MAC header forspecial BSR MAC CE is different from LCID used for truncated and regularSL BSR MAC CE, so that gNB can know that this SL BSR is special SL BSR.gNB will then use information received in special BSR in addition tolast reported regular BSR for scheduling.

In another embodiment, triggered SL BSR is a special SL BSR wherein datavolume of LCG(s) associated with SL LCH(s) for which ‘mode is changedand SL data is available for transmission’ is reported. SL BSR MAC CEfor special SL BSR includes data volume for one or more LCGs wherein foreach reported LCG, ‘buffer size, LCG ID and destination index’ isincluded in special SL BSR. LCID in MAC header for special BSR MAC CE isdifferent from LCID used for truncated and regular SL BSR MAC CE, sothat gNB can know that this SL BSR is special SL BSR. gNB will then useinformation received in special BSR in addition to last reported regularBSR for scheduling.

Method 2

gNB signals scheduling mode (M1 or M2 or both) associated with each SLLCH. The signaling can be via RRC message. Later scheduling modeassociated with one or more SL LCHs is changed by gNB wherein the gNBsends RRC signaling message (or another signaling method such as MAC CE)with updated association between SL LCH(s) and scheduling modes.Scheduling mode associated with one or more SL LCHs can also be changedby UE when criteria to change mode is met. The criteria can be based onSL quality or CBR measurement of SL resources, etc.

FIG. 5 illustrates another embodiment of UE operation when schedulingmode is changed from M2 to M1 for one or more SL LCHs according to anembodiment of the disclosure.

Referring to FIG. 5, UE operation when scheduling mode is changed fromM2 (i.e. UE autonomous Resource Allocation) to M1 (i.e. ScheduledResource Allocation) for one or more SL LCHs at operation 500 is asfollows:

In an embodiment of this method, if SL data (i.e. packets or RLC SDUs)is available for transmission in the RLC entity of SL LCH of adestination and for this SL LCH mode is changed from M2 to M1 atoperation 505, and either priority of this SL LCH is higher thanpriorities of SL LCHs having data available for transmission belongingto same destination at operation 515, or data is not available fortransmission in any SL LCHs belonging to same destination at operation525, UE (i.e. MAC entity in UE) triggers SL BSR at operation 520, atoperation 530. If not, UE does not trigger SL BSR at operation 510, atoperation 535. Note that if above condition is met for multiple SL LCHs,only one SL BSR is triggered.

In an embodiment of this method, if SL data (i.e. packets or PDCP SDUs)is available for transmission in the PDCP entity of SL LCH of adestination and for this SL LCH mode is changed from M2 to M1 atoperation 505, and either priority of this SL LCH is higher thanpriorities of SL LCHs having data available for transmission belongingto same destination at operation 515, or data is not available fortransmission in any SL LCHs belonging to same destination at operation525, UE (i.e. MAC entity in UE) triggers SL BSR at operation 520, atoperation 530. If not, UE does not trigger SL BSR at operation 510, atoperation 535. Note that if above condition is met for multiple SL LCHs,only one SL BSR is triggered.

In another embodiment of this method, if SL data for a SL LCH of adestination for which mode is changed from M2 to M1 and which belongs toan LCG, becomes available to the MAC entity at operation 505, and eitherpriority of this SL LCH is higher than priorities of SL LCHs having dataavailable for transmission belonging to same destination at operation515, or data is not available for transmission in any SL LCHs belongingto same destination at operation 525, UE (i.e. MAC entity in UE)triggers SL BSR at operation 520, at operation 530. If not, UE does nottrigger SL BSR at operation 510, at operation 535. Note that if thiscondition is met for multiple SL LCHs, only one SL BSR is triggered.

In another embodiment of this method, if SL data for a SL LCH of adestination for which mode is changed from M2 to M1, becomes availableto the MAC entity at operation 505, and either priority of this SL LCHis higher than priorities of SL LCHs having data available fortransmission belonging to same destination at operation 515, or data isnot available for transmission in any SL LCHs belonging to samedestination at operation 525, UE (i.e. MAC entity in UE) triggers SL BSRat operation 520, at operation 530. If not, UE does not trigger SL BSRat operation 510, at operation 535. Note that if this condition is metfor multiple SL LCHs, only one SL BSR is triggered.

For the triggered SL BSR, UE includes SL BSR MAC CE in MAC PDU andtransmit it to the gNB using UL SCH resource. If UL SCH resource is notavailable or if UL SCH resource is available but the SL BSR MAC CEcannot be accommodated in the UL SCH resource, UE may also triggerscheduling request wherein scheduling request is sent to gNB using PUCCHresource.

In an embodiment, triggered SL BSR is a regular SL BSR. SL BSR MAC CEfor SL BSR includes data volume for one or more LCGs wherein for eachreported LCG, ‘buffer size, LCG ID and destination index’ is included inSL BSR.

In another embodiment, triggered SL BSR is a truncated SL BSR whereindata volume of LCG(s) associated with SL LCH(s) for which mode ischanged is reported. SL BSR MAC CE for truncated SL BSR includes datavolume for one or more LCGs wherein for each reported LCG, ‘buffer size,LCG ID and destination index’ is included in truncated SL BSR.

In another embodiment, triggered SL BSR is a truncated SL BSR whereindata volume of LCG(s) associated with SL LCH(s) for which ‘mode ischanged and SL data is available for transmission’ is reported. SL BSRMAC CE for truncated SL BSR includes data volume for one or more LCGswherein for each reported LCG, ‘buffer size, LCG ID and destinationindex’ is included in truncated SL BSR.

In another embodiment, triggered SL BSR is a special SL BSR wherein datavolume of LCG(s) associated with SL LCH(s) for which mode is changed isreported. SL BSR MAC CE for special SL BSR includes data volume for oneor more LCGs wherein for each reported LCG, ‘buffer size, LCG ID anddestination index’ is included in special SL BSR. LCID in MAC header forspecial BSR MAC CE is different from LCID used for truncated and regularSL BSR MAC CE, so that gNB can know that this SL BSR is special SL BSR.gNB will then use information received in special BSR in addition tolast reported regular BSR for scheduling.

In another embodiment, triggered SL BSR is a special SL BSR wherein datavolume of LCG(s) associated with SL LCH(s) for which ‘mode is changedand SL data is available for transmission’ is reported. SL BSR MAC CEfor special SL BSR includes data volume for one or more LCGs wherein foreach reported LCG, ‘buffer size, LCG ID and destination index’ isincluded in special SL BSR. LCID in MAC header for special BSR MAC CE isdifferent from LCID used for truncated and regular SL BSR MAC CE, sothat gNB can know that this SL BSR is special SL BSR. gNB will then useinformation received in special BSR in addition to last reported regularBSR for scheduling.

Method 3

gNB signals scheduling mode (M1 or M2 or both) associated with each SLLCH. The signaling can be via RRC message. Later scheduling modeassociated with one or more SL LCHs is changed by gNB wherein the gNBsends RRC signaling message (or another signaling method such as MAC CE)with updated association between SL LCH(s) and scheduling modes.Scheduling mode associated with one or more SL LCHs can also be changedby UE when criteria to change mode is met. The criteria can be based onSL quality or CBR measurement of SL resources, etc.

FIG. 6 illustrates another embodiment of UE operation when schedulingmode is changed from M2 to M1 for one or more SL LCHs according to anembodiment of the disclosure.

FIG. 7 illustrates another embodiment of UE operation when schedulingmode is changed from M2 to M1 for one or more SL LCHs according to anembodiment of the disclosure.

Referring to FIGS. 6 and 7, UE operation when scheduling mode is changedfrom M2 (i.e. UE autonomous Resource Allocation) to M1 (i.e. ScheduledResource Allocation) for one or more SL LCHs (step 600 or step 700) isas follows:

In an embodiment of this method, if the periodic-BSR-TimerSL is runningand remaining timer value is greater than a threshold, UE trigger SLBSR. Threshold is signaled by gNB using RRC signaling.

Referring to FIG. 6, if the periodic-BSR-TimerSL is running andremaining timer value is greater than a threshold at operation 605, UEperform the operation as defined in method 1. Threshold is signaled bygNB using RRC signaling. if SL data is available for transmission for SLLCH for which mode is changed from M2 to M1 at operation 615, UEtriggers SL BSR at operation 625. If not, UE does not trigger SL BSR atoperation 610, at operation 620.

Referring to FIG. 7, if the periodic-BSR-TimerSL is running andremaining timer value is greater than a threshold at operation 705, UEperform the operation as defined in method 2. Threshold is signaled bygNB using RRC signaling. if SL data is available for transmission for SLLCH of a destination and for this SL LCH mode is changed from M2 to M1at operation 715, and either priority of this SL LCH is higher thanpriorities of SL LCHs having data available for transmission belongingto same destination at operation 725, or data is not available fortransmission in any SL LCHs belonging to same destination at operation735, UE triggers SL BSR at operation 730, at operation 740). If not, UEdoes not trigger SL BSR at operation 710, at operation 720, at operation745.

For the triggered SL BSR, UE includes SL BSR MAC CE in MAC PDU andtransmit it to the gNB using UL SCH resource. If UL SCH resource is notavailable or if UL SCH resource is available but the SL BSR MAC CEcannot be accommodated in the UL SCH resource, UE may also triggerscheduling request wherein scheduling request is sent to gNB using PUCCHresource.

Scheduling Mode is Changed from M1 to M2 for One or More SL LCH(s)

It is noted that the methods disclosed in this embodiment are alsoapplicable for the case when scheduling mode is changed from M1+M2 to M2for one or more SL LCH(s).

Method 1

gNB signals scheduling mode (M1 or M2 or both) associated with each SLLCH. The signaling can be via RRC message. Later scheduling modeassociated with one or more SL LCHs is changed by gNB wherein the gNBsends RRC signaling message (or another signaling method such as MAC CE)with updated association between SL LCH(s) and scheduling modes.Scheduling mode associated with one or more SL LCHs can also be changedby UE when criteria to change mode is met. The criteria can be based onSL quality or CBR measurement of SL resources, etc.

FIG. 8 illustrates an embodiment of UE operation when scheduling mode ischanged from M1 to M2 for one or more SL LCHs according to an embodimentof the disclosure.

Referring to FIG. 8, UE operation when scheduling mode is changed fromM1 (i.e. Scheduled Resource Allocation) to M2 (i.e. UE autonomousResource Allocation) for one or more SL LCHs at operation 800 is asfollows:

For the LCG associated with SL LCH of a destination for which mode ischanged from M1 to M2, if there is at least one SL LCH associated withthat LCG for which mode is not changed from M1 to M2 at operation 805,trigger SL BSR at operation 815. Let's say LCH 1, LCH 2, LCH 3 and LCH 4of a destination are mapped to LCG X. LCH 1, LCH 2, LCH 3 and LCH 4 areall mapped to M1. Based on NW/UE trigger scheduling mode is changed forLCH3. Since LCG X is associated with LCH 3 and there are other LCHsassociated with LCGX for which mode is not changed, UE trigger SL BSR.If not, UE does not trigger SL BSR at operation 810.

For the triggered SL BSR, UE includes SL BSR MAC CE in MAC PDU andtransmit it to the gNB using UL SCH resource. If UL SCH resource is notavailable or if UL SCH resource is available but the SL BSR MAC CEcannot be accommodated in the UL SCH resource, UE may also triggerscheduling request wherein scheduling request is sent to gNB using PUCCHresource.

In an embodiment, triggered SL BSR is a regular SL BSR. SL BSR MAC CEfor SL BSR includes data volume for one or more LCGs wherein for eachreported LCG, ‘buffer size, LCG ID and destination index’ is included inSL BSR.

In another embodiment, triggered SL BSR is a truncated SL BSR whereindata volume of following LCGs is reported: LCG associated with SL LCH ofa destination for which mode is changed from M1 to M2. SL BSR MAC CE fortruncated SL BSR includes data volume for one or more LCGs wherein foreach reported LCG, ‘buffer size, LCG ID and destination index’ isincluded in truncated SL BSR.

In another embodiment, triggered SL BSR is a truncated SL BSR whereindata volume of following LCG(s) is reported: LCG associated with SL LCHof a destination for which mode is changed from M1 to M2 and for whichthere is at least one SL LCH associated with that LCG for which mode isnot changed from M1 to M2. SL BSR MAC CE for truncated SL BSR includesdata volume for one or more LCGs wherein for each reported LCG, ‘buffersize, LCG ID and destination index’ is included in truncated SL BSR.

In another embodiment, triggered SL BSR is a special SL BSR wherein datavolume of following LCGs is reported: LCG associated with SL LCH of adestination for which mode is changed from M1 to M2. SL BSR MAC CE forspecial SL BSR includes data volume for one or more LCGs wherein foreach reported LCG, ‘buffer size, LCG ID and destination index’ isincluded in special SL BSR. LCID in MAC header for special BSR MAC CE isdifferent from LCID used for truncated and regular SL BSR MAC CE, sothat gNB can know that this SL BSR is special SL BSR. gNB will then useinformation received in special BSR in addition to last reported regularBSR for scheduling.

In another embodiment, triggered SL BSR is a special SL BSR wherein datavolume of following LCG(s) is reported: LCG associated with SL LCH of adestination for which mode is changed from M1 to M2 and for which thereis at least one SL LCH associated with that LCG for which mode is notchanged from M1 to M2. SL BSR MAC CE for special SL BSR includes datavolume for one or more LCGs wherein for each reported LCG, ‘buffer size,LCG ID and destination index’ is included in special SL BSR. LCID in MACheader for special BSR MAC CE is different from LCID used for truncatedand regular SL BSR MAC CE, so that gNB can know that this SL BSR isspecial SL BSR. gNB will then use information received in special BSR inaddition to last reported regular BSR for scheduling.

Method 2

gNB signals scheduling mode (M1 or M2 or both) associated with each SLLCH. The signaling can be via RRC message. Later scheduling modeassociated with one or more SL LCHs is changed by gNB wherein the gNBsends RRC signaling message (or another signaling method such as MAC CE)with updated association between SL LCH(s) and scheduling modes.Scheduling mode associated with one or more SL LCHs can also be changedby UE when criteria to change mode is met. The criteria can be based onSL quality or CBR measurement of SL resources, etc.

FIG. 9 illustrates another embodiment of UE operation when schedulingmode is changed from M1 to M2 for one or more SL LCHs according to anembodiment of the disclosure.

Referring to FIG. 9, UE operation when scheduling mode is changed fromM1 (i.e. Scheduled Resource Allocation) to M2 (i.e. UE autonomousResource Allocation) for one or more SL LCHs at operation 900 is asfollows:

In an embodiment of this method, if the periodic-BSR-TimerSL is runningand remaining timer value is greater than a threshold, UE trigger SLBSR. Threshold is signaled by gNB using RRC signaling. In anotherembodiment of this method referring to FIG. 9, if theperiodic-BSR-TimerSL is running and remaining timer value is greaterthan a threshold at operation 905, UE perform the operation as definedin method 1. Threshold is signaled by gNB using RRC signaling. For theLCG associated with SL LCH of a destination for which mode is changedfrom M1 to M2, if there is at least one SL LCH associated with that LCGfor which mode is not changed from M1 to M2 at operation 915, trigger SLBSR at operation 925. If not, UE does not trigger SL BSR at operation910, at operation 920.

Preamble Group Handling for Random Access Procedure

In the legacy 4 step contention based random access procedure, UE can beconfigured with two sets of preambles, random access preambles group Aand random access preambles group B. During 4 step contention basedrandom access procedure, for each random access preamble transmission,UE determines the random access preamble group as follows:

1> if Msg3 has not yet been transmitted:

2> if Random Access Preambles group B is configured:

3> if the potential Msg3 size (UL data available for transmission plusMAC header and, where required, MAC CEs) is greater thanra-Msg3SizeGroupA and the pathloss is less than PCMAX (of the ServingCell performing the Random AccessProcedure)—preambleReceivedTargetPower—msg3-DeltaPreamble—messagePowerOffsetGroupB;or

3> if the Random Access procedure was initiated for the CCCH logicalchannel and the CCCH SDU size plus MAC subheader is greater thanra-Msg3SizeGroupA:

4> select the Random Access Preambles group B.

3> else:

4> select the Random Access Preambles group A.

2> else:

3> select the Random Access Preambles group A.

1> else (i.e. Msg3 is being retransmitted):

2> select the same group of Random Access Preambles as was used for theRandom Access Preamble transmission attempt corresponding to the firsttransmission of Msg3.

If Random Access Preambles group B is configured, at least one of theparameters ra-Msg3SizeGroupA, messagePowerOffsetGroupB.msg3-DeltaPreamble and preambleReceivedTargetPower are signaling by gNBin Random access configuration.

2 step random access is also supported in NR. In the 2 step contentionbased random access procedure, UE can be configured with two sets ofpreambles, random access preambles group A and random access preamblesgroup B and two sets of PUSCH resources for MsgA MAC PDU transmission.Before transmitting the MsgA in a 2 step random access, if contentionfree resources are not provided by gNB, UE needs to select the randomaccess preambles group A or B.

Embodiment 1

In one embodiment it is proposed that gNB signals two sets of followingparameters: Message size of group A, power offset for group B, deltapreamble and preamble received target power. Note that these parametersare configured per BWP and signalled to UE using system informationand/or dedicated RRC signaling message. The UE uses the parametersconfigured for the UL BWP on which UE performs random access procedure(i.e. UL BWP on which UE transmits preamble in case of 4 step randomaccess and transmits MsgA in case of 2 step random access).

Set 1 consists of at least one of parameters ra-Msg3SizeGroupA,messagePowerOffsetGroupB. msg3-DeltaPreamble andpreambleReceivedTargetPower. These parameters are used to select randomaccess preambles group for 4 step random access.

Set 2 consists of at least one of parameters ra-MsgASizeGroupA,messagePowerOffsetGroupBMsgA. msgA-DeltaPreamble andpreambleReceivedTargetPowerMsgA. These parameters are used to selectrandom access preambles group for 2 step random access. If any of theseparameters are not configured (in the UL BWP for the random access), UEuses the corresponding parameter from Set 1 (in the UL BWP for therandom access).

For 2 step Random Access Preambles group is selected as follows:

If preambleReceivedTargetPowerMsgA is received from gNB for 2 steprandom access, set PREAMBLE_RECEIVED_TARGET_POWER topreambleReceivedTargetPowerMsgA. Otherwise setPREAMBLE_RECEIVED_TARGET_POWER to preambleReceivedTargetPower.

If msgA-DeltaPreamble is received from gNB for 2 step random access, setMSGA_DELTA_PREAMBLE to msgA-DeltaPreamble. Otherwise setMSGA_DELTA_PREAMBLE to msg3-DeltaPreamble.

If messagePowerOffsetGroupBMsgA is received from gNB for 2 step randomaccess, set MESSAGE_POWER_OFFSET_GROUP_B_MSA tomessagePowerOffsetGroupBMsgA. Otherwise setMESSAGE_POWER_OFFSET_GROUP_B_MSA to messagePowerOffsetGroupB.

if Random Access Preambles group B is configured:

if the potential MsgA size (UL data available for transmission plus MACheader and, where required, MAC CEs) is greater than ra-MsgASizeGroupAand the pathloss is less than PCMAX (of the Serving Cell performing theRandom AccessProcedure)—PREAMBLE_RECEIVED_TARGET_POWER—MSGA_DELTA_PREAMBLE—MESSAGE_POWER_OFFSET_GROUP_B_MSA;or

if the Random Access procedure was initiated for the CCCH logicalchannel and the CCCH SDU size plus MAC subheader is greater thanMSGA_SIZE_GROUP_A:

select the Random Access Preambles group B.

else:

-   -   select the Random Access Preambles group A.

else if Random Access Preambles group B is not configured:

select the Random Access Preambles group A.

The 2 step Random Access Preambles group selection is performed beforethe first transmission of MsgA using contention based random accessresources during random access procedure.

Embodiment 2

Step 0: During the random access procedure initialization, UE firstselects the carrier (SUL or NUL). If the carrier to use for the RandomAccess procedure is explicitly signaled by gNB, UE select the signaledcarrier for performing Random Access procedure. If the carrier to usefor the Random Access procedure is not explicitly signaled; and if theServing Cell for the Random Access procedure is configured withsupplementary uplink and if the RSRP of the downlink pathloss referenceis less than rsrp-ThresholdSSB-SUL: UE select the SUL carrier forperforming Random Access procedure. Otherwise, UE select the NUL carrierfor performing Random Access procedure.

Upon selecting the UL carrier, UE determines the UL and DL BWP forrandom access procedure as specified in section 5.15 of TS 38.321 anddescribed below.

-   -   if PRACH occasions are not configured for the active UL BWP:        switch the active UL BWP to BWP indicated by initialUplinkBWP;        if the Serving Cell is an SpCell: switch the active DL BWP to        BWP indicated by initialDownlinkBWP.    -   if PRACH occasions are configured for the active UL BWP: if the        Serving Cell is an SpCell and if the active DL BWP does not have        the same bwp-Id as the active UL BWP, switch the active DL BWP        to the DL BWP with the same bwp-Id as the active UL BWP.    -   perform the Random Access procedure on the active DL BWP of        SpCell and active UL BWP of this Serving Cell.

UE then determine whether to perform 2 step or 4 step RACH for thisrandom access procedure.

-   -   If this random access procedure is initiated by PDCCH order and        if the ra-PreambleIndex explicitly provided by PDCCH is not        0b000000, UE selects 4 step RACH.    -   else if 2 step contention free random access resources are        signaled by gNB for this random access procedure, UE selects 2        step RACH.    -   else if 4 step contention free random access resources are        signaled by gNB for this random access procedure, UE selects 4        step RACH.    -   else if the UL BWP selected for this random access procedure is        configured with only 2 step RACH resources, UE selects 2 step        RACH.    -   else if the UL BWP selected for this random access procedure is        configured with only 4 step RACH resources, UE selects 4 step        RACH.    -   else if the UL BWP selected for this random access procedure is        configured with both 2 step and 4 step RACH resources,    -   if RSRP of the downlink pathloss reference is below a configured        threshold, UE selects 4 step RACH. Otherwise UE selects 2 step        RACH.

UL carrier for random access procedure is explicitly signaled by gNBduring handover or reconfiguration with sync for 4 step RACH. If gNBwants UE to select NUL for 4 step RACH, it provides 4 step contentionfree random access resources for NUL in reconfiguration message. If gNBwants UE to select SUL for 4 step RACH, it provides 4 step contentionfree random access resources for SUL in reconfiguration message. In anembodiment, UL carrier for 2 step random access procedure is alsoexplicitly signaled by gNB during handover or reconfiguration with sync.If gNB want UE to select NUL for 2 step RACH, it provides 2 stepcontention free random access resources for NUL in reconfigurationmessage. If gNB wants UE to select SUL for 2 step RACH, it provides 2step contention free random access resources for SUL in reconfigurationmessage.

If 2 step contention free random access resources for SUL is signaled bygNB during handover or reconfiguration with sync, UE selects SUL andRACH type selected is 2 step RACH. If 2 step contention free randomaccess resources for NUL is signaled by gNB during handover orreconfiguration with sync, UE selects NUL and RACH type selected is 2step RACH. If 4 step contention free random access resources for SUL issignaled by gNB during handover or reconfiguration with sync, UE selectsSUL and RACH type selected is 4 step RACH. If 4 step contention freerandom access resources for NUL is signaled by gNB during handover orreconfiguration with sync, UE selects NUL and RACH type selected is 4step RACH.

Based on the above criteria, UE has selected 2 step RA procedure. UEinitializes the preamble transmission counter(PREAMBLE_TRANSMISSION_COUNTER) to zero.

Step 1: If contention Free Random Access Resources are provided by gNBand there is at least one SSB/CSI RS having SS-RSRP/CSI-RSRP above athreshold amongst the SSBs/CSI RSs for which contention free randomaccess resources are provided, UE transmit Random Access Preamble inPRACH occasion and MAC PDU in PUSCH Occasion using the assignedcontention free random access resources. Otherwise, UE transmit RandomAccess Preamble in PRACH occasion and MAC PDU in PUSCH Occasion usingthe contention based random access resources. In an embodiment, it ispossible that a valid PUSCH occasion is not available corresponding toselected SSB/CSI-RS and in this case UE skips transmission of MsgA MACPDU. For transmitting Random Access Preamble in PRACH occasion and MACPDU in PUSCH Occasion using the contention based random accessresources, UE selects random access preamble group and then selects arandom access preamble from the selected group in this step. If UE haspreviously selected a preamble random access preamble group during thisrandom access procedure, UE selects the same preamble group. Otherwise,the random access preamble group is selected as follows:

if Random Access Preambles group B is configured:

if the potential MsgA size (UL data available for transmission plus MACheader and, where required, MAC CEs) is greater than ra-MsgASizeGroupAand the pathloss is less than PCMAX (of the Serving Cell performing theRandom AccessProcedure)—PREAMBLE_RECEIVED_TARGET_POWER—MSGA_DELTA_PREAMBLE—MESSAGE_POWER_OFFSET_GROUP_B_MSA;or

if the Random Access procedure was initiated for the CCCH logicalchannel and the CCCH SDU size plus MAC subheader is greater thanMSGA_SIZE_GROUP_A:

select the Random Access Preambles group B.

else:

-   -   select the Random Access Preambles group A.

else if Random Access Preambles group B is not configured:

select the Random Access Preambles group A.

In one embodiment it is proposed that gNB signals two sets of followingparameters: Message size of group A, power offset for group B, deltapreamble and preamble received target power. Note that these parametersare configured per BWP and signalled to UE using system informationand/or dedicated RRC signaling message.

Set 1 consists of at least one of parameters ra-Msg3SizeGroupA,messagePowerOffsetGroupB. msg3-DeltaPreamble andpreambleReceivedTargetPower. These parameters are used to select randomaccess preambles group for 4 step random access.

Set 2 consists of at least one of parameters ra-MsgASizeGroupA,messagePowerOffsetGroupBMsgA. msgA-DeltaPreamble andpreambleReceivedTargetPowerMsgA. These parameters are used to selectrandom access preambles group for 2 step random access. If any of theseparameters are not configured, UE uses the corresponding parameter fromSet 1.

In an embodiment, ra-MsgASizeGroupA is not explicitly signalled. It isequal to the transport block size of the MSGA payload associated withpreamble group A. UE can determine this based on PUSCH resourceconfiguration associated with preamble group A.

For 2 step Random Access Preambles group is selected as follows:

IfpreambleReceivedTargetPowerMsgA is received from gNB for 2 step randomaccess (in the configuration of UL BWP of this random access procedurei.e. in the configuration of UL BWP on which UE transmits MsgA for thisrandom access procedure), set PREAMBLE_RECEIVED_TARGET_POWER topreambleReceivedTargetPowerMsgA. Otherwise setPREAMBLE_RECEIVED_TARGET_POWER topreambleReceivedTargetPower (from theconfiguration of UL BWP of this random access procedure i.e. from theconfiguration of UL BWP on which UE transmits MsgA for this randomaccess procedure).

If msgA-DeltaPreamble is received from gNB for 2 step random access (inthe configuration of UL BWP of this random access procedure i.e. in theconfiguration of UL BWP on which UE transmits MsgA for this randomaccess procedure), set MSGA_DELTA_PREAMBLE to msgA-DeltaPreamble.Otherwise set MSGA_DELTA_PREAMBLE to msg3-DeltaPreamble (from theconfiguration of UL BWP of this random access procedure i.e. from theconfiguration of UL BWP on which UE transmits MsgA for this randomaccess procedure).

If messagePowerOffsetGroupBMsgA is received from gNB for 2 step randomaccess (in the configuration of UL BWP of this random access procedurei.e. in the configuration of UL BWP on which UE transmits MsgA for thisrandom access procedure), set MESSAGE_POWER_OFFSET_GROUP_B_MSA tomessagePowerOffsetGroupBMsgA. Otherwise setMESSAGE_POWER_OFFSET_GROUP_B_MSA to messagePowerOffsetGroupB (from theconfiguration of UL BWP of this random access procedure i.e. from theconfiguration of UL BWP on which UE transmits MsgA for this randomaccess procedure).

Step 2: UE then starts msgB-ResponseWindow and monitor the PDCCH forrandom access response in msgB-ResponseWindow. UE monitors the PDCCH ofthe SpCell for a random access response identified by MSGB-RNTI whilethe msgB-Response Window is running. If C-RNTI MAC CE was included inthe MSGA: UE additionally monitor the PDCCH of the SpCell for randomaccess response identified by the C-RNTI while the msgB-Response Windowis running

Step 3: While msgB-Response Window is running:

If C-RNTI was included in MsgA and UE receives PDCCH addressed to C-RNTIand this random access procedure was initiated for BFR: RAR reception issuccessful. RA procedure is successfully completed. Go to step 8.

Else If C-RNTI was included in MsgA and Time Alignment Timer (TAT)associated with a Primary Timing Advance Group (PTAG) is running and UEreceives PDCCH addressed to C-RNTI and this PDCCH contains UL grant fornew transmission: RAR reception is successful. RA procedure issuccessfully completed. UE releases the 2 step CFRA resources (randomaccess preamble(s), RACH occasions, PUSCH resources) configured (if any)for this random access procedure. Release here means that UE will notuse these resources for subsequent random access procedure. Go to step8. In an embodiment, release operation may not be performed in thiscase, as contention free resources may not be configured for the casewhere PTAG is running and RA is initiated for events other than BFR.

Else If C-RNTI was included in MsgA and TAT timer associated with PTAGis not running and UE receives PDCCH addressed to C-RNTI and DLTransport Block (TB) scheduled by this PDCCH includes Absolute timingadvanced command MAC CE: RAR reception is successful. RA procedure issuccessfully completed. UE releases the 2 step CFRA resources (randomaccess preamble(s), RACH occasions, PUSCH resources) configured (if any)for this random access procedure. Go to step 8. Release here means thatUE will not use these resources for subsequent random access procedure.

Else If UE receives PDCCH addressed to MSGB-RNTI and decoded TB includesfallbackRAR MAC subPDU corresponding to its transmitted preamble: RARreception is successful.

If random access preamble transmitted is contention free random accesspreamble: RA procedure is successfully completed. UE releases the 2 stepCFRA resources (random access preamble(s), RACH occasions, PUSCHresources) configured (if any) for this random access procedure. Go tostep 8. Release here means that UE will not use these resources forsubsequent random access procedure.

Else

Transmit MsgA MAC PDU as Msg3 in UL grant received in fallbackRAR

Start contention resolution timer

Go to step 5

Else If UE receives PDCCH addressed to MSGB-RNTI and decoded TB includessuccessRAR MAC subPDU corresponding to UE's contention resolutionidentity (i.e. contention resolution identity received matches the first48 bits of CCCH SDU transmitted in MsgA): RAR reception is successful.RA procedure is successfully completed. Go to step 8. Note that this isthe case when CCCH SDU is included in MsgA, that is UE is inidle/inactive or performing RRC connection re-establishment. For thesecases contention free resources are not configured, so no need torelease. In an alternate embodiment, UE releases the 2 step CFRAresources (random access preamble(s), RACH occasions, PUSCH resources)configured (if any) for this random access procedure. Release here meansthat UE will not use these resources for subsequent random accessprocedure.

Step 4: If RAR window expires:

Increment preamble transmission counter by 1.

If msgATransMax is configured, and ifPREAMBLE_TRANSMISSION_COUNTER=msgATransMax+1:

Switch to 4 step RA. Go to step 7.

Else:

go to step 1

Step 5: While contention resolution timer is running:

If the Random Access procedure was initiated for beam failure recoveryand the UE receives PDCCH transmission addressed to the C-RNTI; or ifthe Random Access procedure was initiated by a PDCCH order and the UEreceives PDCCH transmission addressed to the C-RNTI; or if the RandomAccess procedure was initiated by the MAC sublayer itself or by the RRCsublayer and the UE receives PDCCH transmission addressed to the C-RNTIand contains a UL grant for a new transmission: Contention Resolution issuccessful; RA procedure is successfully completed. Release 2 step CFRAResources i.e. preambles/ROs/PUSCH Resources configured (if any) forthis RA procedure. Go to step 8. Release here means that UE will not usethese resources for subsequent random access procedure.

Step 6: If contention resolution timer expires:

Increment preamble transmission counter by 1.

If msgATransMax is configured, and ifPREAMBLE_TRANSMISSION_COUNTER=msgATransMax+1:

Switch to 4 step RA. Go to step 7.

Else:

go to step 1

Step 7: perform 4 step RA. If 4 step CFRA resources are configured,these will be released when RA procedure is completed.

During the 4 step RA attempts, UE selects the random access preamblegroup. If random access preamble group was selected during the 2 step RAattempts of this random access procedure, UE shall select the samerandom access preamble group for 4 step RA. Otherwise UE will select therandom access preamble group as follows:

1> if Msg3 has not yet been transmitted:

2> if Random Access Preambles group B is configured:

3> if the potential Msg3 size (UL data available for transmission plusMAC header and, where required, MAC CEs) is greater thanra-Msg3SizeGroupA and the pathloss is less than PCMAX (of the ServingCell performing the Random AccessProcedure)—preambleReceivedTargetPower—msg3-DeltaPreamble—messagePowerOffsetGroupB;or

3> if the Random Access procedure was initiated for the CCCH logicalchannel and the CCCH SDU size plus MAC subheader is greater thanra-Msg3SizeGroupA:

4> select the Random Access Preambles group B.

3> else:

4> select the Random Access Preambles group A.

2> else:

3> select the Random Access Preambles group A.

1> else (i.e. Msg3 is being retransmitted):

2> select the same group of Random Access Preambles as was used for theRandom Access Preamble transmission attempt corresponding to the firsttransmission of Msg3.

Step 8: Stop.

Embodiment 3

For 2 step Random Access Preambles group is selected as follows:

if Random Access Preambles group B is configured:

if the potential MsgA size (UL data available for transmission plus MACheader and, where required, MAC CEs) is greater than ra-MsgASizeGroupAand the power ‘P’ is less than PCMAX (of the Serving Cell performing theRandom Access Procedure); or

if the Random Access procedure was initiated for the CCCH logicalchannel and the CCCH SDU size plus MAC subheader is greater thanMSGA_SIZE_GROUP_A:

select the Random Access Preambles group B.

else:

-   -   select the Random Access Preambles group A.

else if Random Access Preambles group B is not configured:

select the Random Access Preambles group A.

‘P’ is the power required to transmit MsgA MAC PDU using PUSCH resourceconfigured for group B. P is given by:

P=PREAMBLE_RECEIVED_TARGET_POWER+MSGA_DELTA_PUSCH+ALPHA*PL+10log₁₀(2^(μ)·M_(RB,b,f,c) ^(PUSCH))+Δ_(TF,b,f,c)+f_(b,f,c)

‘b’ is the active UL BWP for MsgA transmission, f is the carrier forMsgA transmission and c is the serving cell index of serving cell towhich MsgA is transmitted.

PREAMBLE_RECEIVED_TARGET_POWER is given by preambleReceivedTargetPowersignalled by gNB.

MSGA_DELTA_PUSCH is given by parameter msgADeltaPreamble. IfmsgADeltaPreamble is not signalled by gNB, MSGA_DELTA_PUSCH is given bymsg3-DeltaPreamble signalled by gNB.

APLHA is given by parameter msgA-Alpha. If msgA-Alpha is not signalledby gNB, APLHA is equal to 1

M_(RB,b,f,c) ^(PUSCH) is the bandwidth of the PUSCH resource assignmentexpressed in number of resource blocks for PUSCH transmission occasionon active UL BWP b of carrier f of serving cell c and μ is a SCSconfiguration.

PL is the downlink pathloss calculated as specified in TS 38.213

Δ_(TF,b,f,c)+f_(b,f,c) is calculated as specified in TS 38.213,subclause 7.1.1

In one embodiment, ra-MsgASizeGroupA is not explicitly signaled. It isequal to the transport block size of the MSGA payload associated withpreamble group A. UE can determine this based on PUSCH resourceconfiguration associated with preamble group A.

The 2 step Random Access Preambles group selection is performed beforethe first transmission of MsgA using contention based random accessresources during random access procedure.

FIG. 10 is a block diagram of a terminal according to an embodiment ofthe disclosure.

Referring to FIG. 10, a terminal includes a transceiver 1010, acontroller 1020 and a memory 1030. The controller 1020 may refer to acircuitry, an ASIC, or at least one processor. The transceiver 1010, thecontroller 1020, and the memory 1030 are configured to perform at leastone operation including a combination of operations, which are not inconflict, illustrated in at least one of the drawings, e.g., FIGS. 1-9,or described above. Although the transceiver 1010, the controller 1020,and the memory 1030 are shown as separate entities, they may be realizedas a single entity like a single chip. Alternatively, the transceiver1010, the controller 1020, and the memory 1030 may be electricallyconnected to or coupled with each other.

The transceiver 1010 may transmit and receive signals to and from othernetwork entities, e.g., a base station.

The controller 1020 may control the UE to perform functions according atleast one operation described above.

In an embodiment, the operations of the terminal may be implementedusing the memory 1030 storing corresponding program codes. Specifically,the terminal may be equipped with the memory 1030 to store program codesimplementing desired operations. To perform the desired operations, thecontroller 1020 may read and execute the program codes stored in thememory 1030 by using a processor or a central processing unit (CPU).

FIG. 11 is a block diagram of a base station according to an embodimentof the disclosure.

Referring to FIG. 11, a base station (BS) includes a transceiver 1110, acontroller 1120 and a memory 1130. The controller 1120 may refer to acircuitry, an ASIC, or at least one processor. The transceiver 1110, thecontroller 1120 and the memory 1130 are configured to perform at leastone operation including a combination of operations, which are not inconflict, illustrated in at least one of the drawings, e.g., FIGS. 1-9,or described above. Although the transceiver 1110, the controller 1120,and the memory 1130 are shown as separate entities, they may be realizedas a single entity like a single chip. Alternatively, the transceiver1110, the controller 1120, and the memory 1130 may be electricallyconnected to or coupled with each other.

The transceiver 1110 may transmit and receive signals to and from othernetwork entities, e.g., a terminal.

The controller 1120 may control the BS to perform functions according toat least one operation described above.

In an embodiment, the operations of the BS may be implemented using thememory 1130 storing corresponding program codes. Specifically, the BSmay be equipped with the memory 1130 to store program codes implementingdesired operations. To perform the desired operations, the controller1120 may read and execute the program codes stored in the memory 1130 byusing a processor or a CPU.

While the disclosure has been shown and described with reference tovarious embodiments thereof, it will be understood by those skilled inthe art that various changes in form and details may be made thereinwithout departing from the spirit and scope of the disclosure as definedby the appended claims and their equivalents.

What is claimed is:
 1. A method performed by a terminal for 2-steprandom access procedure in a wireless communication system, the methodcomprising: identifying that contention-free random access resources for2-step random access is not configured; identifying whether one of afirst preamble group or a second preamble group is selected for aprevious random access preamble transmission attempt during the 2-steprandom access procedure; in case that the one of the first preamblegroup or the second preamble group is selected, selecting a samepreamble group used for the previous random access preamble transmissionattempt, for transmitting a contention-based random access preamble on aphysical random access channel (PRACH); and transmitting, to a basestation, a message including the PRACH and a physical uplink sharedchannel (PUSCH).
 2. The method of claim 1, further comprising: in casethat the one of the first preamble group or the second preamble group isnot selected: selecting the first preamble group for transmitting thecontention-based random access preamble on the PRACH in case that thesecond preamble group for the 2-step random access is not configured;and selecting one of the first preamble group or the second preamblegroup for transmitting the contention-based random access preamble onthe PRACH in case that the second preamble group for the 2-step randomaccess is configured.
 3. The method of claim 2, wherein the selecting ofone of the first preamble group or the second preamble group fortransmitting the contention-based random access preamble comprises:selecting the second preamble group in case that a potential size of themessage is greater than a threshold and a pathloss is less than a valuedetermined based on first information on a target power for receivingthe message and second information on a power offset of the messagerelative to the target power.
 4. The method of claim 3, furthercomprising at least one of: acquiring first parameter on the targetpower for receiving the message for the 2-step random access from thebase station, or acquiring second parameter on the power offset of themessage relative to the target power from the base station, wherein thefirst parameter corresponds to the first information and the secondparameter corresponds to the second information.
 5. The method of claim4, wherein, in case that the first parameter is not acquired from thebase station, a third parameter on a target power for receiving amessage 3 for a 4-step random access corresponds to the firstinformation.
 6. The method of claim 4, wherein, in case that the secondparameter is not acquired from the base station, a fourth parameter on apower offset of a message 3 relative to a target power for a 4-steprandom access corresponds to the second information.
 7. The method ofclaim 2, wherein the selecting of one of the first preamble group or thesecond preamble group for transmitting the contention-based randomaccess preamble comprises: selecting the second preamble group in casethat a media access control (MAC) service data unit (SDU) on the messageis associated with a common control channel (CCCH) and a size of the MACSDU with a MAC subheader is greater than a predetermined size.
 8. Aterminal for 2-step random access procedure in a wireless communicationsystem, the terminal comprising: a transceiver; and a controller coupledwith the transceiver and configured to control to: identify thatcontention-free random access resources for 2-step random access is notconfigured, identify whether one of a first preamble group or a secondpreamble group is selected for a previous random access preambletransmission attempt during the 2-step random access procedure, in casethat the one of the first preamble group or the second preamble group isselected, select a same preamble group used for the previous randomaccess preamble transmission attempt, for transmitting acontention-based random access preamble on a physical random accesschannel (PRACH), and transmit, to a base station, a message includingthe PRACH and a physical uplink shared channel (PUSCH).
 9. The terminalof claim 8, wherein the controller is further configured to control to:in case that the one of the first preamble group or the second preamblegroup is not selected: select the first preamble group for transmittingthe contention-based random access preamble on the PRACH in case thatthe second preamble group for the 2-step random access is notconfigured, and select one of the first preamble group or the secondpreamble group for transmitting the contention-based random accesspreamble on the PRACH in case that the second preamble group for the2-step random access is configured.
 10. The terminal of claim 9,wherein, for selecting one of the first preamble group or the secondpreamble group, the controller is further configured to control to:select the second preamble group in case that a potential size of themessage is greater than a threshold and a pathloss is less than a valuedetermined based on first information on a target power for receivingthe message and second information on a power offset of the messagerelative to the target power.
 11. The terminal of claim 10, wherein thecontroller is further configured to control to perform at least one of:acquiring first parameter on the target power for receiving the messagefor the 2-step random access from the base station, or acquiring secondparameter on the power offset of the message relative to the targetpower from the base station, wherein the first parameter corresponds tothe first information and the second parameter corresponds to the secondinformation.
 12. The terminal of claim 11, wherein, in case that thefirst parameter is not acquired from the base station, a third parameteron a target power for receiving a message 3 for a 4-step random accesscorresponds to the first information.
 13. The terminal of claim 11,wherein, in case that the second parameter is not acquired from the basestation, a fourth parameter on a power offset of a message 3 relative toa target power for a 4-step random access corresponds to the secondinformation.
 14. The terminal of claim 9, wherein, for selecting one ofthe first preamble group or the second preamble group, the controller isfurther configured to control to: select the second preamble group incase that a media access control (MAC) service data unit (SDU) on themessage A is associated with a common control channel (CCCH) and a sizeof the MAC SDU with a MAC subheader is greater than a predeterminedsize.